How much more weight did you add? I think the Sig Hog Bipe flying weight is 6.5 - 7.5 lbs. A Saito FA-100 four stroke can handle 7 - 9 lbs. So it would be more than necessary at the normal weight, so a few more ounces would be fine with the FA-100. A Saito FA-125a would make it SCREAM.