I'd say you won't. My largest gas hull is 50" long and uses a 2" offset 90-degree header just because it needs to clear the radio box.
This is inside of my Insane Jersey Skiff to give you and idea. I used the Zippkits transom exhaust kit which you can just butt the silicone running up against the cone but I opted to use a piece of 1/2" ID silicone inside that to seal it up better (the yellow inside).