The nice part about knives. If there is one you don't like, get rid of it and get something more suitable for you. I'd suggest a 16.
The 16 isn't quite the same kind of knife, so its not quite a direct conversion, but I totally agree with you. The "tweeners" (BK15/16/17) have much narrower handles, and may fit the OP's hands better.
If it were me, I'd get a piece of sandpaper and lay it on a piece of glass/countertop/bench/table (anything flat), and sand the scales down slightly. Even just 1/16 - 1/32 off of each side can make a huge difference in how the knife feels.
As I said before, I actually added liners under my BK9's scales to make it thicker/more like the BK2, as the handle was just too narrow. But all it took to make it feel "right" was two 1/32in liners (one under each scale), which really isn't all that much. So yeah, I'd slowly sand them down, making sure that you're not bowing them at all, and stop when you find something comfortable for you :thumbup:.