I strongly recommend using the ROBART 530 RS 90 Degree for main retracts that are Robo-Strut ready and adapting them to use the scale struts offered by Hobby People (for $24.99) designed specifically for retract use on the DH-88 Comet ARF. I also recommend buying the ROBART air control kit and medium pressure vessel. The retracts offered for this model are of unknown manufacturer and my concern was finding replacement parts. The ROBART set-up I have described above is of much higher quality and the ROBART air valve is adjustable. I have this model and yes there are some issues that need to be addressed while "building" this ARf but show me one ARF that the advanced modeler does not have to modify. I have 2 Enya 50SS ringed engines in my model and fly off of grass. I give this model a good "Thumbs-Up"!! Not for the beginner RC pilot though. This model flies and lands "HOT"!!!