My stock mounts work great, although it's always a bit tricky to get the tool perfectly vertical.
Anyway they will never be as good as a set of custom mounts.
At the moment the mounts put pressure on the front and back of the tool, squeezing it far more than I would like.
Also, custom mounts would be able to hold the tool right down at the collar, which has got to be more stable.
I was considering adding a dust shoe as well, but I think my machine's too small to bother.
Anyway it sounds like no one's done any yet, so as soon as I find a new CAD program, that doesn't make me want to tear my haro out, I'll draw some up.