I been doing assisted one arm pull-ups on the Beastmaker for the last few weeks to warm up for weighted deadhangs and it seems to work well as both a warm-up and improving pulling strength.
It depends what edges/level you are working but FWIW the way I do it is to start by using the RH Beastmaker outer slot with my LH and all 4 fingers of my RH on the small crimp below it and then do 3 pull-ups going into a deepish lock each time which I can gauge because my head touches the ceiling. Then I swap sides. For the next set I do a further 2x3 but with just the front3 on the edge. The set after is back3. I am currently finishing by try it with front 2 with a view to progressing to back 2 once I can do 2x3. BTW you need a fair bit of clearance either side of the Beastmaker to do this - more than your average doorway. I did try initially with a pulley system with a foot sling one armed but found this worked better. Hopefully I will be able to one arm the slot eventually.
