I know you said you didn't want an aftermarket exhaust because of the odd gap left after removing the factory setup, but there is a perfect solution.

Carbon fiber belly pan:
http://www.austinracing.info/mall/pr...BON%20BODYWORK

A few videos for you:

http://www.youtube.com/watch?v=Vuax9NaS-hk
http://www.youtube.com/watch?feature...3ff93MUqc&NR=1
http://www.youtube.com/watch?v=9b5aN3d0cvM