My big old Yew self bow has about that much set and it still shoots fine, I've overdrawn it to 31" which hasn't helped.
I would seriously urge you not to mess with a bow you didn't make yourself.
You could very easilly do more harm than good.
If the wood is near it's limits all you will achieve is slight recurve at the tips and more set elsewhere.
Personally I'd leave it well alone, it seems to have plenty of character, and that set may well be the price you pay for it.
Please don't mess with it. If you are actually unhappy with it contact the bowyer.
If someone was complaining about a bow I'd made, my attitude would be, let me see it and I'll advise what is required, if there's a problem I'll fix it. If someone tried to 'fix' one of my bows I'd give 'em short shrift.
Del
Note:- I was slightly confused when you said you measured to the 'back' of the grip, that's why I gave my 'fingers' explanation. I think you mean the
belly of the grip. (I know 'back' sounds right... but it isn't)
BYW I'm an 'Overseas English maker'
!