I had some in a close ratio 4th and a 3:1 ratio 4th and they really performed well. The 3:1 was much better as a single in the 3:1 was as loud as the pair in a regular ported on the same power.
I got 147's out of the pair in the close ratio 4th from a trunk ported through my skipass on ~ 2.5k. Link to the build beow. That number in the OP was on ~ 1,800w.
The 3:1 was .5 sealed/1.5 ported 40sq inof port tuned to 49hz.
TaylorFade's 4th order blowthrough.