I helped fit an Airtec intercooler on a 66 plate Civic Type R. What a nightmare, a poorly thought through upgrade not helped by the crap instructions, that said you may have to cut the undertray. Didn't tell us which bit to cut, where or how much.
Left it off in the end
Good move in leaving it until the next day and look at it with fresh eyes
Incidentally, once we'd got the bumper back on, I went back to the undertray and looked at it carefully and using the old intercooler as a guide and comparing to the new, managed to figure out what bits to cut, but couldn't be arsed taking it all apart again, so it stayed off!!