PrecisionH23a

Im having a hard enough time finding someone that can custom make me a 3" exhaust where the mandrel segments do not crimp on the inside. My question is this, if i use a 2.5"dp and run the 3" exhaust from the end of dp to the very back, how will the 2.5>3" work? I know a full 3" from front to back is the best, but i am just curious how the 2.5>3 will run. Im going to try my damndest to have a custom 3" dp made, but its gonna take a lot of researching. Any info is appreciated, this is for a 94 prelude.