G( DA, NAV, 10)@base P(500)<--- P(500)<---
With no hires can I send ---> (1) [20 minute gap]-->(DA,NAV) then I turn the Nav back then back forward so that [DA,NAV] overlaps with 1 driller DA triggers but then retriggers with the 1 driller before the enemy gets so he can't redirect it in time?

For unkown reasons multiple subs engaging in combat at the same time will result in one of them turning around (at least that's what I have experienced on multiple occasions).