umm.....why spend the money on the stainless tip if it's not going to be seen?
2.5" inlet tip? the inlet for your tip is the size of your exhaust tubing. so...likely 2" inlet is needed.
Check your local specs as to legality of a semi-dumped system.
It'll be a little louder on the inside...but not that much louder compaired to dumped directly after the muffler like myself.
Here's an idea on the "tip" i would run.....