Thanks Lowrider. I estimate the sensitivity somewhere between 95 and 99 db based on the sensitivity of the 416s, from the spec sheet "99db SPL with 1 watt input from warble frequency of 100 to 1600 Hz measure on axis 4' from cone"
As far as footers go - I am looking for short footers, maybe 1" because I designed the cabinet so the woofer/tweeter junction is at my ear level in my listening chair. But that's mostly for aesthetics, not so much bass improvement.