Wanted to follow up with my experience.

3M made schedule changes that made connections impossible. I called B6 and they were able to fix it with plenty of flexibility. I got that agent to give me the 3M PNR and then called 3M for seats.

OLCI worked on B6 when they were the first carrier, but would not let me.pay for a bag so I had.to see an agent. Gave my pre check on the B6 leg but not 3M leg. It did not work on 3M, but evidently it never works on 3M ex-bahamas. When checking in with 3M, I got pre check on their leg (useless), but not on the B6 leg.

Baggage was happily tagged through by an agent in both directions. 3M agent charged the lower B6 fee.

Connections FLL required going from concourse E to C, about a 10 minute covered walk outside. Return via MCO, customs was quick.for US passports, waited about 20 minutes for bags and then returned them to a 3M agent after customs. We went through a little TSA checkpoint after customs and then up an escalator into the JetBlue gasge area -- no train ride to the central terminal.

Would I do it again? yes, though it would be great if OLCI fully worked. The annoyance of the 3M schedule changes would make me consider any reservation tentstive.

FWIW, ELH is a fun airport... No waiting room, but there is a liquor store across the street with some picnic tables.