First the ports on the MSM are only for out of band management so they can't pass normal traffic and you can't add vlans to them.
We have many dual 8810 set up a core aggregations but we use Mlag as all our services are layer 2 only. Best practice and advise is use at least two ports from two separate blades to connect you 8810's together.
Dual MSM's too . Make sure all your cards are from same class because the fabric will only use the lowest card specs so it does you no good to get 128 MSM along with some of the over subscription cards as the tables will still be only the lesser card.