Very nice! And inexpensive as well. My only thought is that a hemisphere or cone shape over the base (point toward back of capsule) would reduce parallel surface reflections, but how to get it inside the basket???
I have one simmilarly modded end address st51. This should be addressed, however i couldn't eliminate effect totally. There is also ring around the capsule which is the part of the grille construction, it affects the response as well.
It's a couple of db boost in 3-5K range. Doesn't sound bad, might be useful for live, but good to be aware of it.