I am maybe surmising it may be either 135.075 or 125.325 from what I can hear of the PBI Feed heading out to WOLFO/PERMT out of FLL/MIA
I haven't monitored that area very much, but I have heard them split that ZMA01 sector north(135.075)/south(125.325), as well as use 123.675 in that area as well. I remember they have also used a Ultra High sector above 135.075, maybe using 125.325 or 123.675 ? They appear to have various sector configurations depending on the traffic.
I guess I am used to the ZNY area when I said it didn't appear to be any high traffic density transiting ZMA/ZJX. Comparably quiet than up here.
JAX is very busy, almost all their High sectors are covered by Ultra High sectors, ZMA not so much and AFAIK they only use Ultra High sectors over their east coast Atlantic sectors.
I sure miss the DX Tuners website, that had good coverage of this area.