Here are three RCU links to RPM readings taken on the glow G90s:
http://www.rcuniverse.com/forum/m_22...key_g90/tm.htm
http://www.rcuniverse.com/forum/m_33.../anchor/tm.htm
http://www.rcuniverse.com/forum/m_39..._1/key_/tm.htm
It would appear that the 13" props are OK for break-in, but 14" and 15" props are more suitable for everyday use. Also, the G90 muffler appears to be quite restrictive. There are a couple of references to drilling out the stinger, and punching out the baffle. Tower Hobbies calls it the "Silent Muffler".
http://www2.towerhobbies.com/cgi-bin...?&I=LXFV93&P=Z
Bruce