Hi Woody - I notice that your post is dated last year, but I do (did) have your very problem with my Ryobi fence.
A parallel ruler will solve your problem (at least mine did). Raise the blade all the way up and place one 'rule' against the blade and the other 'rule' against the fence and while holding the far end of the fence lock it down.
Made my own parallel ruler and I am still using it with good results, pretty sure that any good stationary supply store will have them available.
All you will need to do is replace the 'inner' short legs with longer ones, with mine I can set