I hope experts such as Doug @Rosseforp will also chime in here.
An M5 thread is only .09mm larger than a 10-32 thread and the pitch is almost identical. What this means is that a handle with an M5 thread will fit loosely on a cap with a 10-32 thread, and a handle with a 10-32 thread might fit a cap with a M5 thread, but snugly.
I have made most of my handles to where they will fit both an M5 cap and 10-32 cap, but I have made a few that will fit only a Fatip with it's M4.5 x .75 thread.
Doug