Btw, here is a comparison of a sim I did with the approach mentioned above, in a cab similar to yours, but with only one driver plus a vented back chamber.
The real (half space) measurement is the wavy line. The purple line is the Hornresp export (scaled quarter space; not much different from the og half space export) and the cyan-green line, which is closest to the measurement, is the Hornresp export plus baffle gain exported from Edge. The baffle gain was scaled to half space (twice the baffle area).
These were not gain-matched, but voltage matched, so the final simulation is pretty spot-on with the actual result. I did another design on the same principle and it was within 1db of the predictions.