You can arm One Shot with YES, Grid Rec off.
A trick I found : use patterns. Go back to previous pattern undo. It records all the time, change pattern to stop recording. Defined length. Realtime monitoring with fx (DIR not needed)
Pattern 1 :
T1 Rec trig + Flex trig
T2 Flex trig
T3 Flex trig
T4 Flex trig
Pattern 2:
T1 Flex trig
T2 Rec trig + Flex trig
T3 Flex trig
T4 Flex trig
Pattern 3:
T1 Flex trig
T2 Flex trig
T3 Rec trig + Flex trig
T4 Flex trig
Pattern 4:
T1 Flex trig
T2 Flex trig
T3 Flex trig
T4 Rec Trig + Flex Trig
Pattern 5:
T1 Flex trig
T2 Flex trig
T3 Flex trig
T4 Flex trig