[Freakypen]

If you are using the proper polycarbonate paint it certainly shouldn't flake off- certainly mine don't.
I use the Tamiya polycarbonate spray cans.
Not to state the obvious but make sure you take off the blue overspray film if this is on the side that you want to spray on.
I spray my wings on the underside and I've found that the overspray film on some wings is on this side.
If you spray over this then it will certainly flake off.