I know the flat feet issue has been beat to death. So my feet are flat flat, as in 2x4 lumber flat. I have been trying different boots using my custom insoles to ensure my knees don't kill me but have had major issues with heel slippage when they are in. The insoles raise the heel up just enough that my foot doesn't sit in the heel cup right of every boot I've tried. Has anybody else had a similar issue, and if so a recommendation? And yes I'm removing the factory insole.