Exhaust pipe material vs velocity

[Peter Jackson]

Recap- Smaller exhaust - better low end, torque, chokes at high end
       Larger exhaust - better high end, loss of low end

Reason- Smaller diameter keeps exhaust velocity up but is flow
limited at high end
        Larger diameter is not flow limited at high end but
slows         exhaust velocity down from larger diameter

Question- Would using a more heat resistant material to keep the
heat           in and thus the velocity up, allow a person to run
a           slightly larger diameter exhaust without low end loss?

I am thinking 14 gauge Stainless 304 2.5" vs 16/18 gauge aluminized
2",2.25"?  I will have S3s, HSgen4, CAI.

Thoughts?