Rear door skin and lock

just completely rebuilt a set of doors, frames skins etc. As I have fitted central locking I don’t need the rear door lock. The skin covers the lock so 1 less break in point. However the door lock is very tight on the skin.
My question...
If I cut 5mm or so off the lock barrel the barrel will probably full out. As said the whole mechanism is covered so can’t break in. Unlike the fronts does the lock barrel actually need to in the lock for it to work?
Thanks