Justin, congrats on getting the FWB80. I have an old beat up FWB 80 that's actually marked "US Property". Still outshoots all my other air pistols...The grip should be comfortably snug, but not tight enough where it feels unnatural. Of course you can just buy the next size larger grip, but should want to alter your existing grip, here's what worked for me.
I just went through this with a FAS target pistol I just bought. First, put the bottom palm shelf back on and adjust the grip to get it as comfortable as you can, then lock up all screws.
Hold the pistol like you would normally. The grip will be tight on your hand. Then take a pencil, and make small marks where it feels the tightest. Also, closely examine your hand as its holding the pistol. Look at the natural curves and contact points of your hand. You can see and feel what has to be removed. On my FAS I had to take about a 3/16" off the top of the palm shelf, in a gentle arc, to "decompress" my hand. Also removed some more wood around the side/top of my thumb.
Remove some wood , as necessary with a Dremel or other rotary tool, then re-mark where it feels tight after that, and so on, and so on...Of course, where there's little or no contact, just leave alone.
As you remove wood, it will become very messy, but also will immediately start to feel more comfortable. Then, when satisfied, you can finish the job with fine sandpaper & match the stippling, if the grip was stippled. I used a dull ice pick on the FAS grip and it came out perfect. Good luck, you can do this.
