www.nsrca.org has an airplane triming chart. compare the plane's performance to that chart.

My guess is you have a wing warp that hasn't been properly taken care of. what are the aileron positions when the RX and TX are on... and the plane has been trimmed for level flight? If they are left aileron down and right alieron up... you probably have a warp.

Another possibility is... you need more airspeed before lifting it off the ground. However, if that was the problem, I would expect your correction with aileron to just make things worse, resulting in the plane snap-rolling inverted and diving into the dirt. Taikng off too slow can make you think the ailerons are working backwards. (in a way they are... because adverse yaw and the tip-stall combined turns the plane sharply the opposite of the desired direction)

The last possibility I can think of is cross-correction of aileron and rudder. The rudder is more effective than aileron at low speed and would turn the plane one way... then you build speed and correct with the ailerons. So if the rudder is offset one way, and the ailerons the other... you have cross-corrected. (which could have the ailerons offset as in the first case... or in the opposite direction)

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Note that the NSRCA trim chart assumes the plane is a Pattern Competition model... and a plane with a flat bottom or semi-symetrical airfoil will not behave the same in the dive tests. (nor will a lot of older Pattern designs from the 1970's and earlier...) If it tends to pull out of a dive toward level flight... its probably OK on your model.