MegaExo BB7000 replacement options
 

Recently I picked up a new FSA crankset for our tandem which came with FSA BB7000 BBs.
The BB shells on the tandem are both 68BSA and used to have UN-26 cartridges when I was running a crankset with square tapers.

My wife and I were riding tonight and more than ever the tandem seemed like it was lugging along. I had to replace a bearing in the rear hub anyway, so I pulled the chains to check out the cranks and BBs. While smooth running they have some resistance to them. Noticeably more resistance than any of my other bikes. On our mountain tandem which has 68mm threaded shells, the cranks sans chain spin very freely. So I'm going to put in new BBs and see if it makes a difference.

These BBs have a spacer on each side which appears to give an effective width of 73mm. I can mic them easy enough.
In reading, it looks like the MegaExo shaft is 24mm. Again, I can pull one of them and mic it.

Any suggestions on a freer spinning BB?