Large framed/chassis sport ATVs are the Yamaha 700/660 Raptor and Honda 700xx I think Kawasaki has a large chassis sport ATV as well.
The pure sport 450s I think are considered smaller Mid size chassis.
Here is the dementions of a Mid chassis 450 vs a larger 700 chassis. 2011 Yamaha Raptor 700R ATVs
the 450 is wider put not a tall and long.
Seems like the Kawi 700 is more roomy then the Raptor. http://www.atvreviewnetwork.com/enth...e2=54321&go=Go
The Honda 700xx is a nice size as well http://www.atvreviewnetwork.com/enth...e2=58128&go=Go