Unpacked the ribbon tweeters and did a test fit. Have 1/2" on either side of the tweeter to take up to get it to fit, since the slot was sized for the BG Neo3.
The height is correct for one tweeter to match the length for 2 - BG Neo10's, so that will work correctly for stacking them.
Easiest thing would be filler so I do not have to drill new holes in the top and bottom header to move the one 1"x2"x87" oak strip. The tweeter screws will match the existing width. Back to Lowes I go to look.
A very open mesh grill material for around the tweeters is here as well and I can possibly wrap that and the tweeter with the extra width material to hold it together before screwing down the arrays.
The dspMusik RevD 8 channel crossover unit is here as well, so that will be going in instead of the RevC originally in use.