I am not in a spot to be able to confidently tell you the bolt dia and thread, sorry.
I do remember it is the fine UNF thread for the diameter. I had some NOS AN bolts in the bin that fit the hub. Just can't remember the diameter.
But...... I did want to mention that I did the back plate jigging like you mentioned and wound up with the top of the top cowl too high. I suspect it is the weight of the prop but I have never done the differential sag measurements to confirm it. (I feel better if I can blame it on something other than me just screwing up, so I may never measure it)
It was off position right away, not after many hrs of running and it really has not changed in 600 hrs.
You might want to put the prop on just once before making that final cut.
RV-7A: Flying since April 15, 2012. 690hrs
YIO-360-M1B, mags, CS, GRT EX and WS H1s & A/P, Navworx
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