Almighty,
I would absolutely
NOT do this for the following reasons:
1)
Home resale value--this will look like (and sound like) a rube-goldberg solution of the worst order.
2)
Other Better & Inexpensive Options--Even inexpensive 5.25" or 6.5" Kevlar in-walls, such as Monoprice's, are WAY better than the 1.8lb, SB-AFC95 speakers you intend to install and are very inexpensive at ~$45 a PAIR!!
Take your pick from this page:
http://www.monoprice.com/products/subdepartment.asp?c_id=109&cp_id=10837
3)
Fit & Finish--To adequately install the speaker to the stud inside the wall will require a hole larger than the ~4"x5" size of the speaker--fit & finsih of the end product will not be pleasing.
4)
Bad Sound--The sound will be crap, due to the speakers, the install, and the odd resonances of this wall partial enclosure.
As you said "Sac Up" and spend the $45--way worth it!!
XEagleDriver