I'm wondering what the effect of the cupped bill is on crankbait actions in general.
Does it tighten their wobble, help them run more true, make them run deeper, do nothing at all?
I recently tried (again) to make a Fat Rap copy with PVC trim board.
After making the belly a little deeper to lower the center of gravity as a way to make up for less buoyancy (it worked) I moved to shaping the bill.
The original Fat Rap bill has a V shape, which I duplicated in past attempts by bending the 1/8" lexan I use in a vice, with two spacers at the edges of the bill, and one in the middle on the opposite side. When I closed the vice, it did bend the lexan, but it stressed it and eventually caused fault lines.
So this time, I hollowed out a piece of my left over PVC with the narrower end of my belt sander, heated the bill with my heat gun, and used the handle of an exacto knife to force the middle of the bill down into the hollowed out PVC, which was clamped in my vise.
It worked. The Fat Rap swims with a tight wiggle, and doesn't roll at higher speeds, which is why I lowered the belly in the first place.
I know Hazmail routinely shapes his bills with hot oil and nesting dies, but I was too lazy to do that much work.
And the heat gun/hollow form worked out great.
So I'm thinking about cupping the bills in some of my deeper divers, but I was hoping someone here has already tried it, or, at least, knows ahead of time if it works, and what kind of effect it produces.