1) Isn't Thunder Tiger 65 an airbleed carb? Most engines nowadays have no problem mounted inverted, except for airbleed 2-stroke. There is no low speed fuel limiter valve; rather, low speed adjustment is done via controlling the air inlet (airbleed) hole size to mix with fixed amount of fuel intake @ idle. If fuel tank is higher than carb inlet nipple, gravity will draw the fuel down, which is more fuel than the some airbleed can mix.

2) I am not sure about Cline regulator, but I know for sure Perry pump will not work, as you will just flood the carb at idle, again, for the same reason caused by air bleed carb.

3) To adjust, open the airbleed adjustment as large as you can, and see if it will stay idle. If not, try lowering the tank so it is completely below the carb. Try this low profile tank:

http://www2.towerhobbies.com/cgi-bin...?&I=LXK835&P=0