I have Renthal 672 fatbars on my Tuoldo - they are 10mm lower, much more than that and the switchgear hits the tank on full lock.
They help get a bit more weight onto the front wheel, but I have learned to move forward as well as across the saddle to help. Someone on the AF1 forum made the comment about "trying to kiss the mirrors" when cornering the T's.
TBH Tuono's aren't about top speed, I get mullered down the straights at Cadwell by the litre Jap 4's, but usually catch back up on corner entry speed into Coppice, and under braking for Park etc. To me the Tuono has the perfect balance of hooligan ability, with the ease of dawdling in comfort if you want to.