Skid T....interesting dilemma you have there as you want the max power for your track day!
(I seem to recall we had our Full Monty Ivanising done on the same day.)
I'm not bothered about legal volume tbh & don't do track days!
Could you add a small amount of extra baffle to your aftermarket can for the day? Or as PieEater says, maybe it needs repacking.
Packing is a very simple job & the material is very cheap at a bike parts shop....a good place to start perhaps.
My can strap is on wrongly Panther, I can't seem to find one that fits the Viper any better!
My can is now looking & sounding better, a nice bit of popping on decel. (one of my favourite sounds
) & more volume generally BUT I might
just be tempted still to take off another 2".
Once I settle on the length I plan to make a heat shield for the link pipe & can, more for appearance than anything else...I really do dislike regular looking exhausts!