Decatting a Fireblade

Been talking to a few people about providing decat pipes for RR4 to RR7 and 08 to 11 Blades. I have a set of RR4 headers that I can remove the cat from the cat can or cut the can off and replace with stainless tube . Just need someone to try it when it's done. Mique, what sort of performance increase do you reckon by removing the cat from the can???
Hoping someone with a post 2008 Blade can lend me their old slab cat/silencer so I can take some measurements or ride down here so I can measure it on the bike. Will provide food and drink ???
Will be visiting Mique on Sunday or Monday, so may be able to pop around to somebodies gaff to do some measuring, if we take the belly pan off???

De-catting the standard pipe was done on impulse and found the engine note much deeper at tick over and revved quicker than before. It was only half the job as the four pipes have a restrictor each before it reaches the collector box with those removed I expect a power gain of 3-4 bhp at the back wheel. The standard pipes are quite heavy which robs an engine of its bhp, a full race system useing lighter gauge metals a power gain of 6-8 bhp can be expected these however cost a lot of bucks.