I have now got my build of Fairmount Alpine under way and deliberated about a Stern thruster well I have finale done the deed and fitted one. Its a bit tight and I had to put two skins of ply on either side of the keel. Cutting down the the thruster leaves very little room for the O ring seal .If you see Bent Immertreu build ,he has pictures on google, I made a template out of two mil ply of the thruster body centered it on the existing hole in the keel and cut out the minimum of the wood this was done after it was all glued up .I would recommend to make a template of the keel shape before it is glued up so you have a pattern to go over where it has been cut out . I also redrilled the thruster body and and made new mounting hole for the motor using two mil nuts and bolts, captivating the nuts with Epoxy .I have pictures I will post when I work out how to move them about the computer.