I've ordered couple sets of 9x5... I was used it on my 401k tricopter with 800kv motors and AUW 900gr. That size is a bit small for my current t-copter with AUW 1.1kg. Well, I am building quad and think those props will fit it well.
Hmmm ... I recently tried some 10x6 counter-rotating pairs from hobbyking. Quite a bit of balancing was required and they weren't a good match for my dt-750 based quad (not enough lift). It flies much better with GWS RD 1147 (slow-flyers) but these are not available as counter-rotating pairs, so tilting is required. I'd like to try 12x3.8 slow-flyers with my DT-750s but APC are too heavy and too expensive. Does anyone have experience with GWS RD 12x6 slow-flyers and DT-750 ?
Giantcod here in the UK are now stocking a good range of forward and reversed props. and they are cheap!! Downside, a bit fragive in a strike situation!!! jpc