The Metronome

I'm considering using a pair of Tannoy ~4" dual concentric drivers - the ones used in the Autograph Mini - in Metronome cabs. The obvious one(s) to choose as a starting point, based on the size of the driver, would be the original one designed for the FE108e or the one designed for the FE127e. The Tannoy driver is a tad deeper than the Fostex - about 78mm from the back of the mounting flange - but the smaller cab could work if I use an additional thickness on the front face (possibly just a "power bulge"). The larger cab would be easier to mount the driver in. Any opinions as to the most fruitful direction to take here, and what cab dimensions I should be looking at? I've measured the midbass driver params using DATS V2 - see pic.
tannoy autograph mini midbass.jpg
 
Looking at #18, one aspect of this quadratic taper design that surprises me is that it appears from what is said that it is a 1/4 wave resonator. I ask because my understanding is that this expansion results in a half wave fundamental resonance. (Like a saxophone)
Many apologies if this has been covered, or it is a dumb question.
 
A line open at one end is a quarter-wave resonator, one open at both ends or none is a half-wave resonator.
.........though when tapered it's some form of 'closed cone', i.e. a 1/2 WL resonator with a 1/4 WL fundamental. It's this seeming conundrum that me n' MJK are perennially at 'head knocking' odds with in describing them in that his '1/4 WL pipe' is technically correct whereas I prefer to use '1/2 WL resonator' as it describes it better to the casual DIYer and provide a link to graphically 'prove' both and let the 'gentle reader' choose his own.
 
.........though when tapered it's some form of 'closed cone', i.e. a 1/2 WL resonator with a 1/4 WL fundamental. It's this seeming conundrum that me n' MJK are perennially at 'head knocking' odds with in describing them in that his '1/4 WL pipe' is technically correct whereas I prefer to use '1/2 WL resonator' as it describes it better to the casual DIYer and provide a link to graphically 'prove' both and let the 'gentle reader' choose his own.
I am I admit anything but an expert, but that link seems to me to show clearly that a closed cone is a half wave resonator. It has the same length and harmonics as the open pipe.

I have previously asked why a saxophone's lowest note is an octave higher than a clarinet's of the same length: The answer:

Because a saxophone is conical, and a clarinet is tubular.

Apparently (for reasons I cannot pretend to understand) this makes the saxophone a half wave resonator, and a clarinet a 1/4 wave resonator.