I was rethinking your post, Semi, and I'm starting to think; Geez does it really matter how fast or slow you deviate from the original tune? If you put your own style to it and it sounds good, what does it matter?

And, I have actually heard many performers change speeds mid-sing after bridges, chorus, etc. it's really not a crime to make a correction unless it's REALLY noticable.

Dont be so hung up on the speed, as long as it sounds good to you and the audience dig's it, your in good shape.

Al