My Heath Robinson way of cutting a trainer insole down the middle is not perfect, I know this and would not pretend otherwise.
Depending on the thickness of the insole it could be that if you tried the idea you will feel the insert trainer edge as you walk, in my experience, however, it won't be for long, the edge tends to flatten out over time and because I wear my Sorbothane's over the top I don't feel the edges anyway. I might do if I wore a thin insole over the top? If I use a thicker half insole I usually trim the edge with a Stanley knife. What I have never worked out accurately is, how much additional height do I actually need to make my feet walk neutrally? The 1/4" of the Rehband's height I suspect is the same as most half insoles? I've guessed and for me, my feet feel OK even on a long day's walk. The only pair of boots that I have which shows that my half insole idea works for me is my cheap pair from Decathlon. I walked for two weeks in the Pyrenees last year, with half insoles in, plus my Sorbothane's and the sole wear is very even right across the boot.
I've actually worked my way through a few half insoles trying to find the best one for me and I'm hoping that by spring next year my new Berghaus boots will show that they are wearing evenly. If not I would have wasted my time.