If youre dragging the rudder at an angle to keep on course, its *usually* not a problem of the rudder but errant sail shaping/trim or at the very worst a mast rake or rigging tension problem.
If in fact you are dragging the rudder, modifying the rudder is only treating symptoms rather than addressing the cause.

The probable two chief causes of adverse helm (with *woven dacron sails*) are 1. insufficient mainsail halyard tension after raising the 'main'; 2. too loose forestay.

A. If you dont fully 'stretch out' the luff boltrope in the woven dacron mainsail (by about 1" for every 10 ft. of luff length ...'after' raising that sail), the point at which the maximum draft in the sail occurs will be far aft of normal and which causes two things to happen - draft aft = weather helm; and/or, the leech will be closed/'hooked up to weather' = aggressive heeling.
B. a too loose forestay will cause draft aft and hooked up leech on a jib - lessened inability to point, aggressive heeling with 'slow' boat, and the boat 'skidding' off to leeward instead of pointing. Such is usually the result of an improperly tuned/tensioned rigging system. If the forestay isnt at ~15% tension for 'normal' condition and which a sailmaker *expects* when designing and cutting a sail, all 'crazy' helm problems can develop.
Here's probably one of the very best rig tuning guides on the net if this is a rig problem .. dont 'guess' when it comes to rig tuning, sail SHAPE depends on precise rig tension: http://www.riggingandsails.com/pdf/selden-tuning.pdf .... especially look for mast 'pre-bend', also needed to properly set the mainsail shape.

If either of A or B is the case, then suggest at least 'trying' these 2 items if in fact youre in need of 'weather helm', etc. correction. and if either of these issues cant correct the 'helm problem', then and only then consider to re-rake the mast, ... before 'redesigning' the rudder:
• http://forums.sbo.sailboatowners.com/showthread.php?t=120970 posting #1
• http://www.ftp.tognews.com/GoogleFiles/Matching%20Luff%20Hollow.pdf

If your mainsail is woven dacron; probably 98% of cruising sailors simply do not *properly raise* such sails, and simply live with a $#itty helm problem.

THEN if your rudder is not working correctly .... eg. 'sucking air' etc., then get back to the group for 'mechanical suggestions'.

hope this helps, let us know what happens.
:^)))))