I also have trimmed the bolster down on the Davis lock. It is quite thick as it comes from them.
It required a bit of careful grinding on the frizzen as well.
If you are going to file down the bolster to make it more narrow, you may find that the mainspring now interferes with the barrel as you inlet the lock, depending on your barrel size.
Several of us working using that lock at WKU onChristians Spring rifles had to modify the mainspring. It was easy to do, and it does not seem to weaken the Spring enough to affect the function of the lock.
I can post pictures if you find that you need to modify the Spring.
Norm.