Here's a thin plate I make from punch metal. Its heavier than foil, but thin enough to be cut with scissors. I have yet to find a cut mold that will not close on this stuff. The super fry shown here was done using it. I mostly just hand pour whichever side I want the separate color and then shot the other color to finish. I'll shoot baits for tail colors, then trim the tails and re-set them in the mold. I hand pour the belly section right up to the tail, clamp it up and pump the tops. I end up with a three color bait. I'll sometimes short pour the back and the belly different colors then shoot a center color that gets me the same tail color.
I know DF hand pours some too. Honestly the molds are way more versatile by hand pouring than by using plate and if "natural" is intended the hand pouring allows for the lack of an exact line...nothing in nature is that exact.
I think all of the home-spun baits are great looking, split colors or not. Find a way and work with it. It doesn't take long to be making baits that make store-bought look like they are made in a kindergarten class.