Ok I didn't realise the opti was a V6. I'm aware of the chatter about the DF 140 output, but I thought that had been disproved, although having a quick look on the web I couldn't find anything definitive.
Did find some comments that the setup is pretty sensitive to props and needs to be mounted with the cav plate 2-3 inches above the bottom which seems a bit higher than other setups.
Also seems that many people feel the need to run them near WOT, which is OK 'cause they are quiet, economical and have a 5 year warrantee.
But I'm getting a pessimistic feeling that I'm going to get a lot more from it.