I've had the "4", "0" & now "6" <7disk> I'm running a T-76 bb Q-trim .69a/r 4 bolt turbo. I like to street drive my car and its really a handful with this setup on pump gas/street tires. The only downside that I can see w/the loose converter is slippage at the track...although I do lock it in 3rd gear. For around town I love this setup although I do have a spare .81 a/r turbine housing to try at some point.
IMO the best bang for the buck would be "0" pump configuration (not as much slippage/plenty of stallspeed for a smaller turbo).....I tried "O" w/the T-76 & .81 a/r housing and wasn't real content w/it on the street.....so I purchased the smaller turbine housing and had the converter loosened........now I wish I would have just changed the turbine housing