If you are only using 125 grain tips, you can easily get field tips that are the same diameter as the shafts. When using broadheads, the ferrule is usually wider than the shaft. Use the proper size bor broadhead adapter ring. This makes the difference minimal. Pulling broadheads out of the target is not an issue, as you are usually shooting into foam. The only issues that you run into is if you are shooting into a bag with field tips that are too wide. You can't get field tips that are the same diameter in the heavier weights. Usually the best that you can do is get 5/16 tapered field tips. Once again, the broadhead adapter rings(BAR) make up the difference. As far as your setup goes, With only 125 grain tips, I think that you probably would need the 500 spine, unless you plan on leaving your arrows very long.