Intake runners? Custom!

Getting ready to fab a manifold (friend is helping me) for Suzuki GSXR 750 independant throttle bodies --> m10 1.8 head/2.0 block (Mega Squirt). I'm pretty excited!
(I need to do this before I get the rebuild)

So, How long are the intake runners??????
I've been doing ?retarted? math and have come up with 12.5 inches. I'm looking for low end torque not a 700mph car.

Any suggestions??

BTW I think the ITB are 42mm

I heard that the longer the runners, the more torque you get...up to a certain limit though.