I installed a Mitsubishi Kuro Kage graphite shaft in my Mizuno JPX 825 6 iron without realizing the OEM steelshaft I took out was taper tipped and the Mitsubishi shaft was parallel tipped (I initially measured the OEM shaft above the ferrel at .370).  I must have sanded the shaft down enough so it would fit and it did bottom out in the hosel when I assembled the club.  This was a trial so when I called to order additional shafts I learned of my error.  Question, can I do the additional sanding on the rest of the shafts to make them fit and would that cause a problem with the shaft performance.  Would you recommend boring out the hosel for the parallel tip and is that a service you offer and if so, what is the charge?

I’ll just leave a comment as it looks like your looking for Golfworks to do the work.
Yes, you can sand the shafts down towards the very tip to get them to fit. This will not compromise the shaft. I have done this in the past with no problems.
I prefer to drill out the hosels, there is more variety of shafts at .370 Parallel then .355 Taper.

Sanding is a little more cost effective.