Making a new exhaust

[Digifox]

Well i'm not happy with the way my exhaust LOOKS..i love the can and the way it sounds...
But after i swap out the rear end of my EX250 for a 94+ EX500 (170/60-17)
I want to do a little "bolt on" fab work.

By modding my Full Yoshimura exhaust in to a "under" or side seat exhaust

Like this guy did on his 500
http://bikepics.com/pictures/916186/

Only i want to make mine like a mid pipe in being it slips into place with out any modification to the can or header.

Also i will use softer bent tubing. that will be supported by the "old" mount for the yoshi can
and again where the Passenger pegs went(where the can will mount with a special bracket)

And seeing that the ex500 rearsets and frame form more of a "one-piece" the "mid-pipe" will fallow the body lines.

I have a rough sketch sitting in front of me right now i will finish up a few more sketches and scan it.

And whats the longer exhaust going to do to my performance and tune?