[A-PEN68 Development Log] Episode 7: From A-PEN65 to A-PEN68

A-PEN68 Prototype Model

── The Search for the Ultimate 8-Gram Balance: Redesigning the A-PEN 68

Even though I was consistently pinning quality bass on the 65mm version of our topwater pencil, pivoting back to punishing field tests on saltwater bream revealed an entirely new set of engineering hurdles.

In its 65mm footprint, the prototype maxed out in the high 6-gram range. It was hovering just under that critical 7-gram barrier, and after putting it through its paces, our conclusion was definitive: it was still too light.

When you're approaching topwater bream fishing (Chining) with baitcasting tackle, a sub-7g lure simply doesn't cut it. It leaves you wanting more control. Feedback from specialized pro shops like Flagship and Top Butler, as well as elite local angler TK Takuya, all pointed to the same metric: "We need this platform to sit right around the 8-gram mark."

Faced with that reality, we made the call to upscale the footprint. We decided to expand the injection-molded body profile out to 68mm.

Early prototypes of the A-PEN65 (foreground) and A-PEN68 (background)

Pushing Past 8 Grams: The Buoyancy Paradox

Initially, our approach was straightforward. We took our foundational A-PEN 90 geometry, downscaled it to a 60mm baseline, and then applied a proportional scale-up to 65mm and 68mm to build our test samples.

The A-PEN68 was modified by repurposing the fundamental principles of buoyancy learned during the development of the Zelfas 133F, gradually increasing its buoyancy.

However, scaling a lure up isn't just about changing numbers on a blueprint; it shifts the entire hydrodynamics. We had to alter the internal chamber layout, importing core buoyancy principles we unlocked during the engineering of our Xelphas 133F swimbait, meticulously carving out internal air space to maximize lift.

By the spring of 2025, armed with the new 68mm footprint and a overhauled internal cavity, our field testing in the saltwater trenches began in earnest. We focused on the absolute epicenters of the Japanese topwater bream scene: the Yodo and Muko Rivers. To push the bait to its absolute limits, we teamed up with TK Takuya, an iconic angler in the Kansai light-game scene, introduced to us by Top Butler.

In early April 2025, we dropped into the Muko River for a heavy testing session.

We unboxed the first-generation A-PEN 68 prototypes. As we rigged up, we debated the conditions: "How are they going to react to the change in water temp today?"

I handed Takuya a spread of different A-PEN 68 test models, featuring varying weight configurations, distinct one-knock rattle notes, and high-pitch internal glass bead arrays. We ran them hard through multiple currents, trading notes on every single cast.

The feedback was immediate and clear cut:

• The Weight Dilemma: We absolutely needed more mass for long-distance casting ballistics.
  

• The Buoyancy Trap: Adding more raw lead to the existing chamber meant some prototypes sat too low in the water film, causing them to stall on the pause.
  

• The Shoreline Factor: Given the steep banks and rip-rap configurations of rivers like the Yodo and Muko, a sinking or overly sub-surface resting posture was a dealbreaker.
  

• The Action Equation: We needed to increase the physical weight for distance, but simultaneously make the bait easier to slide and walk-the-dog with less rod effort.
  

If we stayed trapped within the limits of the current body thickness, these demands were completely contradictory. You can't add weight, keep the exact same silhouette, and increase buoyancy. It's a physics bottleneck.

My mind was caught in a loop: I wanted to preserve the sleek, classic profile of the original A-PEN 90, but the math told me that to increase the internal air volume—and get the buoyancy we needed—we had no choice but to thicken the bait's midsection.

TK Takuya made his first catch with an early prototype of the A-PEN68.

The Spark of Certainty

As we wrestled with these layout issues, we shifted downstream to a new run. A few casts into the new spot, it happened right before our eyes.

Takuya tracked his A-PEN 68 prototype along a seam, and BOOM—a gorgeous, hard-fighting Yellowfin Bream (Kibire) absolutely annihilated the bait on the surface.

Seeing that silver flank breach the surface film and violently choke the prototype right next to me was electric. Up until that exact moment, I hadn't landed a fish on the 68mm prototype myself. Watching the lure work flawlessly under the hands of an elite angler turned all my internal doubts into absolute certainty.

“This is it. The A-PEN 68 pattern is real. This lure is going to revolutionize topwater light game.”

That single catch lit a fire under me to master this style of fishing. We spent the rest of the day grinding out casts, breaking down micro-adjustments on the bank, and sorting through engineering fixes one variable at a time.

During that session, I triggered several massive blowups myself but failed to get the hooks to pin. Yet, those missed opportunities were invaluable data points. I began to develop a hyper-specific feel for the water: “Okay, if I trace this specific depth contour and cross this current line, they will rise for it.”

But to consistently reach those precise, far-side strike zones from the bank, we needed more casting distance.

The developmental priority shifted into clear focus. We had to prioritize raw casting distance and effortless walking action over a hyper-slender bite silhouette.

That day on the Muko River wasn't just a lesson in bream fishing; it was a powerful reminder of what matters most when designing a hard bait built specifically for shore-based, walk-the-bank angling.

And those missed hookups? That lingering frustration was the exact trigger I needed. It flipped a switch inside me. From that week forward, I was out on the mudflats and riverbanks twice a week, every week, ruthlessly optimizing the real-world performance of the A-PEN 68.

In the next chapter, we'll dive into the breakthrough session on the Yodo River, where the A-PEN 68 finally pinned its very first official black bream, kicking off a year-long obsession with topwater game.

Stay tuned.