RE: Cermark F16 w/ air retracts?
call me old school but I prefer a non spring retract because of the speed in which the gear is cycled up/down. the only way I've been able to slow a spring loaded gear down is to put a heck of a bunch of restrictors on all lines and on the forward retracting gears they tend to not want to pull up at flight speeds. if you don't mind that slamming down, sounds like you hit a bird in mid-air, then spring assisted gears are wonderful things. regular checks for leaks and fixing any leak prevents 99% of the necessity of a spring. on a side note, your system should hold air indefinitely, at 120 psi (what i leak test at) mine loose no pressure at all over a 12-24 hr period. over the week between flights mine maintain the pressure they had on last landing.
kc