Rodma / Dave,
I read (I think in Rockfax Sport Climing +) that a good quick hit endurance training session would be an 1hr feet-on campusing, IIRC the recommendation for starting off was;
1.1/2 - 2mins, repeatedly doing - L1R1, L3, R4, L4, R3, L1, R1, R3, L4, R4, L3, R1, L1.............
1min Rest and repeat with the aim of doing this for the full 1hr or until your forearms explode.
I guess that if there is a gain to be made in a specific area by varying the position then what I am thinking about is an optimum postion for maximum gain. I dont plan on doing many of these sessions, just once a week during 4week cycle as a supplimentary.