Guillow's P-40 RC Conversion
I have flown three of the Czech foam Me109s, which are very similar in size, maybe a hair smaller.
All three had 049's. One had rudder and elevator only. While it did fly, rudder is inappropriate for a fighter, and it was not terribly satisfying. One had a TD049 and aileron and elevator. Just great! The last one had all four channels and a golden bee RC. The throttle let you breathe a little.
I would sheet the whole thing with 1/16 or 1/32, tissue it(he is totally right...tissue and dope is much lighter (and stronger) than dope alone) and definitely do ailerons. Even strip ailerons would be better than rudder.
Keep this in mind, too. If you ARE using only rudder, you MUST reduce the free flight dihedrel, lest you get horrible dutch roll with the slightest rudder input. Ask me how I know!
Fiberglass is too heavy on this scale, forget it.
Also, look into a lighter battery pack. Weight really counts, and those servos are not really light. Good luck!