Hi Tim, we're in a similar position it seems. I have a pair of Audiopulse Revo 15's that I'm trying to decide on enclosures for. I actually would prefer LLT but I'm but sure of a couple of things. First, did you have your TC 2000 down-firing or front-firing? I've read and been told that it's best to front-fire these drivers but I'm not sure if that's true. Next, I'm wondering the shape of the enclosure you used. I have 6" aeroports that I'm using and I'm not sure if it's best to fire the port up if the driver is down-firing, for example. Seems like higher frequencies would escape from the port as well if the opening faces the back of the driver. What about wall damping material - did you use any and does it make a big difference? I'm thinking of about 11 ft^3 tuned to around 15 Hz.
Just a thought with regard to your mid-size enclosure build. Maybe something like the MFW-15 from AV123. Those aren't too big and are tuned to around 16 Hz, according to Mark Shifter (I actually spoke with him personally!) Plus, it's a proven design...