Conversion to air retracts using Robart 606 HD at 85 degree. The 606 is almost a drop-in solution. 3/16 wire. Little Dremel work on the hardwood rails. Fill the former wholes with tooth picks and epoxy. Also use some Dremel work on the wheel wells to accommodate the air cylinder. Heat up the retract wire with a propane flame in order to bend them at the same angle. In an first attempt I tried to install the air tank on top of the wing. More useful is the solution to put the air tank inside the fuselage along with the valve as shown in the photo. 2 additional air-restrictors prevent the gear from popping up or down too fast and with too much kinetic force.

This solution is extremely well and I can highly recommend the use of the 606.