I'm pleased to confirm the compatibility of the tonewood amp/X brace with both the 'D-hole' and 'clown mouth'/oval hole Selmer style guitars.
The D-hole is simple enough, I have a rather large hand & can still easily get it in there to place the X-brace.
The oval hole presents more of a challenge- the X-brace can be "rolled" in sideways without much difficulty, but placement over bracing in the lower belly of the guitar is a bit fussy-
I can't get my hand in there to place the X-brace permanently with double stick tape- I maneuver the brace over the lower middle brace, and then center it using the tonewood amp's magnets to drag the brace where i want it.
My guitars have magnetic pickups and BigTone bridge piezos- the magnetic pickups sound better, but i wouldn't rule out the piezo if one has access to an external preamp.
Once it's in place, it sounds brilliant! Much more fun to practice alone and peck out new tunes, the delay makes a fine swinging metronome, and the busking/outdoor playing aspect has a whole new 3rd dimension that grabs passersby- the farther off the beaten path, the better!
Thank you so much for the tip! I have received this question before, but haven't tested myself or heard of any confirmed installs on Gypsy style guitars.
We'd love to see a video if you feel so inclined!