Sprint sports exhaust downpipes

[Aleco]

Hi guys, bit of a random question.
What size pipes are people running on a sports or uprated downpipes on a Sprint.
I'm having an exhaust made but the guy is concerned about enlarging the downpipes and then having a lot of heat soak into the cabin as they'll be very close to the bulkhead.
What experiences do other people have on this?

[Aleco]

I just searched the forum and found the sports exhaust to be 42mm. Which if my maths isn't way off is 1 5/8"

Should have searched before posting!