A3SPD I would say that altitude definitely does matter. We are at about 600 feet MSL here in San Antonio which does wonders for performance. I had heard the Cline regulator was necessary if you mount the fuel tank on the CG and could not get adequate fuel draw. My tank is mounted right behind the firewall and fuel draw is fine without the regulator. I'm not really a 3D person, more into precision aerobatics, so the 20x10 Menz works fine for me at this altitude. The guys that do a lot of 3D here use the APC 20x8.

jmw