One of the nice things about the Gold Tip 3555's is that you can add supplemental weights to the front and back of the shaft. With a 45 lb bow, you will mainly be adding weights to the front of the shaft, to weaken the spine. If it gets a little too weak (nock left for a RH shooter), then you can add a 20 grain weight to the back to stiffen it up a little.
So what I would expect you will end up with is a combination of 50 grain and 20 grain weights on the front, and maybe nothing or a 20 grain weight on the back. I shoot 145 grain points and broadheads, but it will work just as well with 125 grain points and broadheads; you will just have to add more internal weights than I would.
There is no particular reason not to trim the Gold Tips to whatever length you want, since you can compensate for the length by adding internal weights. For example, if I were tuning a 3555 for a new bow, the first thing I would do is to cut the shaft to 29" for my 28" draw length.
I use the same hot melt glue used for aluminum adapters. If I want to remove an adapter, I just hold the tip, front or back, in boiling water for 15 seconds or so and then pull it out with pliers.
You will find that when you shoot the bare shafts, you will lose a front adapter and point into the target unless you fasten it in somehow, and the same for the rear: that bright thing you noticed out of the corner of your eye was your nock flying off the shaft. Some folks wrap the adapter with teflon tape used in PVC pipe fittings, but I just put a speck of hot melt on the adapter. Both methods work fine.