In my opinion, 29" is as far as I'd go with a 64" ntn length. Plus, in looking at the string angle at the nocks in your full draw picture above, you seem to be very close to 90 degrees (if not just a touch more on the upper limb.) If it doesn't already, it will probably stack at anything more than what you're pulling now. I'd say you've got a nice looking bow right now, and if it's shooting great, I'd stay put. Again, just my $.02. I'm sure some other folks can shed some clearer light on the subject.