Hi Serge,

I responded to your email so hopefully that answered your question. 25 mm is good from what I recall. We used the header and canister setup from 3W with the 3W 85 motor. To fine tune the fit I simply heat up the header gently and evenly with a propane torch and bend it to the proper position to line up with the canister. Works like a champ and very easy to do. Get a buddy to help hold the plane or motor steady when you do this.