Jeff,
When you say your jib has a luff in it - do you mean it is luffing or developing a knuckle in the cloth that is not filling just behind the forestay?

It can be caused by forestay sag, or the jib not being cut for the amount of forestay sag that is created when under load. Rigging the boat a little tighter may help as can a little more luff tension.
If you are rigging the boat tightly then check the dolphin striker and make sure it is tight and deflecting the main beam up a little when the boat is not rigged.
If you want to move the sheeting position of the jib back and can't, raking the mast back will change the balance between leach tension and foot tension a little.
I doubt the mast rake will fix the problem but without seeing can't know. It would give you something to play with that may help you work out the sollution.
Regards,
Phill