Gruffydd ap llywelyn still king of Wales post 1066

What if Gruffydd ap llywelyn had kept Wales United under his rule, perhaps by staying on the right side of harold godwinson, up to and beyond the battle of Hastings? How would he deal with the Normans? Would welsh unity and independence be sustained for the mean while or would the Norman barons win?
 
If Gruffydd was on Harold's side, isn't it possible that he might have lent his support to Harold Godwinson during the Norman invasion? I don't know how much Welsh participation there was OTL, but this might just be enough to tip the balance completely in Harold's favor.
 
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