When an Acro Sport II is built to plans the trailing edge of the lower wing hangs slightly below the bottom longeron making the wing root fairing more difficult to make than it should be. I added a former to the bottom tube of the fuselage to get the belly a little lower. Thats it just behind the rear spar fitting.
I also made the firewall in such a way to provide a tunnel for the cooling air. This allowed a different line for the sheet metal to follow that allowed the gear attach fittings to be inside the fuselage and create a nice line under the bottom that should reduce parasite drag and aid in cooling. The gaps normally found at the rear of the cowling have been closed off to reduce cooling drag. I'm not trying to make it fast, just trying to keep it from being any slower than it has to be.