I don't think the rudder is really going to help much in a high yo-yo unless you are near stall speed. The plane will just want to snap back to its velocity vector and you will end up pulling an awkward, high drag turn of sorts.
My advice would be to to really emphasize the 'high' part of the yo-yo and use a lot of vertical. Learn to judge how close to stalling you need to be for the rudder to do anything for you (swing the tail around).
Once you get a feel for this kind of stuff it can really help your reversals (at least it did me).
Need a nice E advantage over your target to be pulling any maneuvers that involve stalls though.
IMHO the rudder is more useful in lining up shots and forcing overshoots
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cmorris