ORIGINAL: TFOX
With your poundage lowered as you have it,the spine is within spec so I wouldn't worry about it,your broadheads should be telling you that.
Inserts are roughly 1" in length,some shorter and some longer,I believe the ACC inserts are slightly shorter.
Did you use hotmelt to install the inserts?That is the preferred method for installing ACC inserts.If so,then you should be able to heat a field tip with it installed and remove the inserts and then cut,then reinstall.
I didn't build these arrows, I had a shop build them (I've since acquired the tools to build my own, but I would rather keep this set for as long as possible since they're perfectly good ACCS, and I still have 16 of them), so I'm not sure what they used for the inserts. I knew you could heat the hot melt, but you have to be careful not to heat close to the shaft, but I never got around to trying. I have a bum shaft I could try on, though. You mentioned that I was in spec, but even after turning down the poundage, when I was BH tuning, I was still hitting just slightly left of FPs. It wasn't terribly off, but I could never get it to come together (unless I lowered the poundage even more, but I opted not to do that this season). Now that hunting season is over, and target is yet to fully begin, I figured now was the best time to get the situation remedied.