Cmon magnus, post the pics dude !!!
So the 12 inch over is for straighline (you might want to add that to your other thread mate!)
Re the pipe it, will run? no wuckas, why wouldnt it?
And the 3 foot flame will be WAY cool.
But mate you are turning this into a show/drag bike I take it?
And I am also guessing you are in the US ?? (bonneville

)
...and also log onto a dedicated ZX12R website for these sort of questions.
Lot of 12 riders here who will reply dont worry

but these are the sort of questions that some of your "buddies" might be able to answer better (from the good stuff I have sifteed from a LOT of shit I have read on Zx12R.rog) or other "Straighline" forums...
Glad to have you here mate
Might want to go to Introductions too....