On control surface gap, the best amount is 0, zip, none, nothing, not a sheet of paper, nada

You don't want ANY air taking a "short cut" from one side of the surface to the other, espeically on the ailerons. Air will go from the high pressure under the wing to the low pressure above it any way it can.

Take a bit of covering or packing tape, and seal the gap.

The easiest way to do it is from the bottom of the wing with packing tape or heat-shrink covering. Disconnect your control rod, and force the control surface as far as it can move, opening the gap as far as you can get it, then get the tape or covering strip as far up in the hinge gap as you can, and stick it really well to the aileron and the TE of the wing.

You only have to do one side, top or bottom, and it doesn't have to be pretty. As long as it doesn't make the surface hard to move.

Sealing the ailerons will also make your trims stay better, reduce the possibilty of flutter at high speeds, and reduce trim changes with airspeed changes.

On anything beyond a trainer, it's a no-brainer, seal the gap