RE: Royal B17 build
I used a set of Spring Air retracts with 5/32 wire struts and Robart strut covers. I mounted the plates for the gear at the correct angle for the down location and then put in stops to have then retract to the correct position. Since air holds them up, they can be stopped anywhere. If you get new retracts, 70 degrees is about the correct angle for a B-17. I have a 120" Wescraft that I will be using 70 degree Spring Air 400 series retracts in.