The GP .42 would be a good engine. However, one word of caution, this engine is VERY tight and needs longer than normal break in for it to have a reliable idle and hold a full throttle setting. I personally prefer an engine that takes longer to break in because I feel it will last longer (provided break in done correctly). OS 8 or OS 3 plug, 15% nitro, 9.5x6 or 9x6 or 9x7 prop will get this engine to hit its powerband (old article from one of the rc mags did a story on .40 sized engines the the .42 shows a tuned exhaust response with slightly smaller props which allows it to rev up to 15,000)

I am currently using LA .40s and I'm getting rid of them. They don't have much power and a .25FX is equally powerful. I'm replacing the LA .40s with two GMS .32s and expecting better performance. I was considering the GP .42 but got a great deal on the GMSs. Another engine I own and am very impressed with is the Leo .28. I have one on an AT-6 and it spins a 9x6 prop faster than my LA .40. I highly recommend it and think it also be a good choice for a twinstar.


BTW, if you got some flight time under your belt, try these modifications:

Don't build the wing with all of that dihedral. Reduce it by 1/2 and you'll get an an airplane that rolls better.

Increase aileron size! I have 1.5 inch ailerons and roll rate is much better.

You can easily mod the nacelles to accept 8 ounce tanks for increased flight time. I had to increase the nacelle height and use micro servos for the throttle, not much weight gain.

Use functional weight to balance aircraft. I've owned 4 of these airplanes (I always end up selling them to someone who makes me an offer I can't refuse). All 4 of mine were tail heavy, even with LA .40 engines in the nacelles. I put my battery as far forward and used a 1300 mah pack.

The plastic nose cone will eventually crack as will the plastic abc covers. You should glass the inside of the cone or use the cone as a mold to scratch build a new fiberglass one.

Also, if you wish to save yourself the trouble down the road, REMOVE ALL OF THAT LOUSY STICK ON COVERING AND COVER IT WITH ULTRACOAT OR EQUIVALENT COVERING. You'll save yourself some trouble down the road since the covering will peel back at the seams (which appear to leech black glue goo when exposed to exhaust residue). Covering is normally good for 1/2 season flying (15-25 flights) before it starts showing some ugly wear and tear.