Hmmm. The bubinga and purpleheart combo for the front and back plates will be pretty reflective, which will definitely help the articulation in an 8-string.
I'm assuming you're running something similar to the Alembic style neck construction and, since you're using it elsewhere, will be using purpleheart instead of ebony or walnut for the interior lams on the neck. If that's true, you'll have a hair less solidity in the lows than you'd get with ebony. The relatively short span you'd be adding with the bubinga and maple racing stripes shouldn't affect the neck resonance to any great degree, though. (If you were using ebony, the bubinga and maple racing stripes might soften the bottom end a bit because of the extra mass in the last 1/4 wavelength. With a PH neck, the extra mass should result in more of the same sound.)
Where the largest effect will be, of course, is in the lateral transmission between the neck core and the body wings. There will be a few more glue joints in the path. _That_ isn't much of an issue with a neck-through; especially in the Alembic style. The single-truss model eliminates most of the body's effect on the sound, other than very minor top reflection back into the strings. And, as mentioned above, that'll effect the upper octave half of the 8-string set more than the regular bass register.
So, no, it shouldn't be a detriment. You'll affect things more by whether you chamber the wings or not, and by how much, if you do.
How wide is your bubinga, anyway? Gilmer Wood (gilmerwood.com) has some spectacular (I mean, mind-blowingly exhibition grade) quilted bubinga. Very resonably priced, too. You may want to look into saving what you have for a future project...
