How to do a cut through

[bahnspl 0]

I know more about the cutting. that is fine. But say I want to do a massive wall. how do I account for flex between the bed and the cab. I would bring it into the cab just an inch and baffle it inside the cab. will it be ok or will there be too much flex.This will be a FULL cut through. window and all. I hear the boot the fits between the cab and bed/shell is EXPENSIVE. how much are we talking? just an est. 200? or 1000?