How would 2 Hitec 5645 servos for the ail. and 3 hitec 5985 for rud and vators work for a WH extra 28%?

That would do quite well !!!! Should have no problems with that.

should I go 5955 on rudder and 5985 everything else. How is that

Thats great !! But for just a little more you could have the 55s and have servos for when you move up to the bigger birds. But the 85s and the 55 on the Rudder would be plenty!!

There has been a lot written about centering issues with the 5645's. I had problems with mine.

I too tried the Hitec 5645s and found the centering to be less than
desireable. Roboto's suggestion is valid. Buying 5955s for all of
the control surfaces allows you to grow into a larger model without
having to purchase new servos. If you do not intend to go larger
at any time, then this point is mute. Read closely, alot of the posts
on this site and you'll see "bigger is better" quite often.

Gerald