What kit are you building?..Gene barton makes retracts for a C-130..have installed mine and with operating doors on the mains....using a robart retract gear for the nose wheels..no doorsWas planning on using 4 Mag's 30 4-strokes,but plane is going to heavier than I thought it would be..have switched to Mag's 36 2 strokes..all engines will be inverted.....breaking them in now....maybe by fall, it will be ready for test flights...going to fly in the primer stage,and if everything goes right,will paint it over the winter and spring,next year...good luck