Thanks for coming here, didn't want to clog up that guys thread.
To do a TMM, you usually have to make it a 2.5 way XO, which is what I ended up doing here. The advantage of a 2.5 way the way I've done it is the woofer is boundary loaded, so tons of bass output. It also helps to minimize the floor reflection and ceiling reflection to a lesser extent, but doesn't do it quite as well as the MTM. It also has the practical advantage of not being as tall. This was quite important to me. A disadvantage of 2.5way is XO complexity and it robs some effeciency out of the midrange. I find the effeciency to not be an issue. Effeciency matters most at 100hz. This is where the baffle step losses are happening, sound tracks are demanding, etc.
An MTM on the other hand will have more vertical directivity (assuming not a 2.5 way with the MTM) so it'll actually do a better job at reducing floor and ceiling reflections. But as far as bass is concerned, both woofers are in full space (sorta). So it won't have quite the oomph in the bass department as my setup. It's also very tall and tippy. Another draw back of it not being 2.5way is you can get lobing, or nulls, in the vertical direction. Especially with such a large spacing between the woofers. Generally, the bigger the speaker the harder this is to deal with. The 10" size is generally ok, even with a 1500hz XO (Cinema 10 Max). But that does have nulls beyond 20 degrees vertically. But a 12", even if crossing down around 1000hz (quite low) would be worse. Then at 15" it's pretty much impossible. You'll get nulls even 10 degrees off probably. That's with the SEOS which is quite short. Most waveguides are taller than the SEOS.
Hope that helps.