I also have a TP p-47, the way I fix my cowl was by inserting small pieces of the plastic nylon push roads that is used for the throttle, made the screw holes a little bigger then inserted the small pieces, I'm using servo screws, they will never come out with this fix, I've done this before a few times with great results.

Recently I ordered from RTL washers that have rubber on one side, these are great for cowls as they absorb the vibrations coming from the engines, these are very small and combined with the servo screws they are superb at holding a cowl in place.

http://www.rtlfasteners.com/RC/bw.html