I used to have one of those, great flying plane at 9 1/2 to 10 lbs. Has a really wicked stall if you get too slow, like most corsairs. I would think the side carb would be the best choice (just my opinion). If you go with a rear carb, the firewall would have to be moved way back or a deep pocket. The firewall is attached to the fuse sides. I wonder if the firewall would be durable since most gassers like an engine box built that is extended into the fuse and anchored to fuse formers. The rcfg web site shows a total width of 5.98" and a height of 5.6" for the side exhaust. I measured my spare cowl at 7.5" diameter at the firewall. Might work. Maybe with a wrap around rear dump muffler.
Edwin