I did an experiment on an OS FT120 last year just to see how much more oil would remain in the crankcase if the engine were run in the inverted position (vent facing up). In the upright mounted position (vent facing down) the crankcase retained approx 2cc of oil, in the inverted mounted position (vent facing up) approx 3cc.
Point being, if oil drainage is a concern one can either change the vent location to a higher position or run a vent line loop over the top of the engine without I'll effect.
Last edited by Glowgeek; 03-01-2023 at 03:52 AM.