Full Flow Filters
Oil drain back? can be addressed by how you route your hoses or put a loop/ hump in them, making a natural barrier for gravity flowback, there a heck of a lot of buggys out there with lots of extra cooling, hoses, etc. must not be too much of a problem. Just don't rev the engine up @ start up until the oil system is fully functioning.
Jim, Hum....It appears I may be over thinking the issue of calc'ing oil capacity and any drainback issues, for 1st startup. I'll figure what a 1 ft section of hose holds, multiply times the total length and add 1 qt for the filter, plus the normal 1600 oil capacity (5.3pts) then what that comes out to is what i'll put in the engine at the first startup. Crank the motor, with the coil wire is off until I get oil pressure. Then start the engine, keeping the rpms low until the pressure is up and constant. I think I have it.............. Thanks for your assistance in getting me thinking "normally" again! But i'm not sure what "normal" is.... Dan
When I initially filled the oil after building and installing the engine and full flow filter. I poured 1 qt of oil in the filter (on the bench) then screwed it onto the adapter. I poured 1 1/2qts. into the engine to fill the 1 1/2 qt. aftermarket sump then I poured the 5 1/2 pints in the engine, that is the engine capacity. I ran the engine then filled the engine to the bottom line on the dipstick. All in all it holds about 4 1/2 quarts. The buggy can sit all winter and the oil is still at the bottom line on the dipstick, so there is no drain back happening. As far as my braided lines chafing, I made UHMW spacers that fit between the hoses at the ties. The spacers allow about 1/16" between hoses. My sandrail has had the braided lines tied together since 1980...How long does it take to wear the hoses out 
I made the spacers because I heard about the wear factor and didn't want to take the chance on the Manx.
I made the spacers because I heard about the wear factor and didn't want to take the chance on the Manx.