Today one of the Saranna prototypes has been on a field trip.
Had pretty bad conditions with enviromential noise, but at least got a few good groundplane measurements of the bass response. This is spliced with a rear measurement to get a somewhat more accurate measurement of the port contribution, not sure if it's still 100% accurate. Taken at 1.5m. Looks pretty even at least.
The response also looks like something that should match room gain pretty well, and give a pretty flat in-room response in the lowest octaves.
Disclaimer: This will probably not be the final response, but a flat response like this is a good starting point for further tuning. Crossover to the coax is around 170hz here I think, as one can see, that is pretty seamless.