T Folts,
Ok...no expert, but one thing I learned through a lot of work, mistakes and phone calls years back to OL, is that indeed, WHATEVER you do to the bare, you ALSO do to the fletched.
The whole process is "diagnosis by comparison" between fletched and bare!!
If they're showing weak, you can take a sliver of anything... toothpick, etc or just use elect. tape, to build up the sideplate...same effect as shortening...
...and much safer. As Dad used to say to me as a kid, "cut it 3 times and it's still too short, huh, kid?"
The key, OL used to say, is to be as far away from the target as you can still get measurable groups! If you're not grouping either bare of fletched...move closer till you do. Then start diagnosis.
Remember, shortening arrow, reducing point weight or increasing sideplate thickness corrects weak spine. Lengthening arrow, decreasing sideplate thickness or increasing point weight corrects stiff spine.
I messed with sideplate a lot, after ruining a bunch of shafts cutting them prematurely. Then once I get it corrected and KNOW that is the issue, shooting good groups with the adjustments made to sideplate, then....only then, do I ever CUT arrows!
Other neat thing with using sideplate corrections is that as I learned to use more back tension and "worked the bag" I found my draw increased. Thankfully, then my arrows weren't all cut too short..just reversed the sideplate material changes.