Woody,
Can you take some pics of any numbers that you find on the backs ( of the paper cones belonging to your 414Z woofs ) and then post them here. Thanks!
In my opinion, ( re; box size ) you shouldn't use a woofer/box size alignment that yields a Qtc number any less than [ .5 ] and that "re-purposed" Flamenco box will ( I fear ) do just that ( ie; I think it's too large for your woofers ).
- Going less than critically damped, would ultimately lead to compromised mid transients with looser bass than I like ( IME of course ) from a woofer with such a light cone and moving assembly ( MMD ).
To proceed properly, someone needs to measure a 414Z and get some accurate TS numbers ( & that someone should be you since you have the woofers and it's your project ) .
You can buy a little gizmo ( from Parts Express called .
DATS V2 ) that'll do TS measurements for you.
Post the numbers here and we can proceed .