A 91 four stroke flew my BS60 very well. If I remember correctly the finished plane weighed 8 pounds, plus or minus a couple of ounces.

This model tends to "build" nose heavy based on everything I have read and that was my experience. With an OS 91 four stroke, tail wheel, and rx pack several inches behind the wing saddle, mine still needed around 2 ounces on the tail.

If you want to use a two stroke to try to save a little nose weight, and do not want to wait for the TH 75, the GMS 76 and SK 90 two strokes are both available for about 100 dollars
http://www3.omnimodels.com/cgi-bin/w...I=GMEG1076&P=0
http://www.atsrcplanes.com/skengines.htm