Not having flown the Gnat since 1975, I vaguely recall STUPRECCC (for hydraulic failure):
S - Speed below 400/ M0.85
T - Trim (feel trim) to the Ideal sector on the FTPI
U - Unlock the elevators, checking 2 clicks, white band and 'ELEV' caption.
P - Power (hydraulic) cock - OFF
R - Raise the standby trim guard
E - Exhaust the pitch accumulator (1.5 to 2.5 deg TPI with u/c up, 5.5 to 6.5 with u/c down), then the aileron accumulator
C- Check elevator response
C - Check TPI response using s'by trim switches nose-up/nose-down
C - Changeover switches (Mod 399) - select
Then maintain the control column at the 'load free central' position using stick top switches to set pitch attitude, control column to hold attitude with unlocked elevators. With u/c down before landing, set 3 deg TPI and confirm a push force reqired to maintain level flight; relax push force to flare.
And CUBSTUNT (for AC/DC failure):
C - Cabin altimeter cock to 'Static'
U - S'by UHF ON
B - Boost pump OFF
S - Speed below 300/M0.7
T - Trim to ideal sector
U - Unlock elevators (2 clicks, white band, 'ELEV' caption on)
N - Non essential electrics OFF
T - Transponder to 7700