Anyone fitting should leave original belts in place as well. Not sure if they did when new from the factory but while the harness is a real sense of occasion paying at toll booths etc are a pain in the ****. Had then in my Exige and they were great but a pain in those type curcumstances.
I know £2400 was on the option which as you say for Maserati wasn't bad but if you went to get one from them now is it a lot more as an accessory. Can you still get them from Maserati ?
The roll bar is still in the Eurospares catalogue. I would have thought it would be a big job to get one fitted though.