I am going to do the same...make it loose weight! I got my MB290 engine ready to run. I checked spark with plug out. It was great just hand flipping it. I put the spark plug in and give her a good flip or 2. It fired hard enough to loosen the G38 prop adapter. I thought this may happen. Can someone give me the thread size of the shaft. I think it may be 8MMx 1.00. I got to know this for sure. I only got 2-3 precut, but not tapped aluminum pieces to mess up. Thanks Capt,n[:-] ....... Edited to add photo