Just open the needles for up going gear. We have had no problems, the UP valve does require a leak free system to operate (any bleed through on the cylinders and it won't work)
Biggest thing is people taking off too fast, pulling hard (climbing) and expect the gear to work against 2-3 g! Even on short grass strips I rarely reach full power on take-off, on a runway I'm normally breaking ground at 2/3rds throttle on a P-120SX!
The angled out leg doors with good airspeed will cause problems...even the full scale has a max speed for gear actuation

Dave