Re twinstar brushed on a 3s lipo, I converted mine using a 3200 mah 3s and just needed a bit ot weight in the nose to make it balance.
Much better performance but it kept throwing the Gunther props, so I bought some prop adaptors and fitted those with some 5 x 3 props. Again great performance but one motor only lasted about 10 flights before it gave up.
Great flyers though so if you are going down this route, either look at a brushless up grade or speak with Puffin Models about the new Mig Brushed motors specifically for 3s lipo's.