Dave,
Not sure why no one has posted a reply, must be all coming back from the NATs and need a rest. Anyway, I will give my two cents. The bladder approach is the simplest, slightly higher pressure approach. You need a fine needle valve thread, need to allow clearance inside the fuse for the full diameter of the inflated tank, the bladder could break but you can usually see this coming, need to fuel proof the inside of the ship, need to use a starter to start. This approach has been used since the 1950's and works. Crankcase pressure on the other hand has been used since the late 1960's. It allows the tank to be constructed within the pan and once the needle is set it should be close all the time. I believe you would use a coffin style tank with the pressure line located near the front as a uniflow. This is the same layout for straight suction. Hopefully some of the guys using this approach can jump in and show a sketch of the tank layout. Sizing is around 1 1/4oz?
Best, DennisT