A throttle curve IS usually needed in order for the throttle to feel linear and respond to your every click accordingly. You can do this mechanically with linkage, but the computer radios really spoil us with their abilities. Setup your travel for the max you can in the radio, and adjust mechanically as best you can, then finish off with the throttle curve, this will give you the best resolution. You might also be simply having a problem with the pressure sensor hole on the diaphragm plate (cover on the carb with a hole in it). as the plane moves through the air, the flow over and around this hole changes, and thus tricks the carb into thinking the air pressure is different, and the carb reacts accordingly. Try removing the plate, and simply rotating it into a different position to see if that helps. If not, a brass nipple can be attached to this hole, with a run of gas line going into the fuse, where the pressure is more constant. Keep us posted!

Chad