ORIGINAL: GBR2
Why not use it without cutting the cowl first and see if it works. No sense cutting the cowl unless it is really needed. I've got a G26 mounting in a Pacific Aeromodels Monocoupe with no velocity stack and the engine runs fine. The carb is totally within the cowl.
Deja Vu [:-], weird, I just told someone that same thing the other day. Just not about the Moncoupe