Turbo manifolds

[CMF_RTK]

Hey guys/girls

I am doing a deal with a mate of mine;
- I'm doing a time belt change for exchange for my mate to weld me up a turbo manifold.

I am wondering what is a good thickness is for the main manifold piece that attaches to the head?

I am thinking getting a 12-15 mm think

What are your guys thoughts? And opinions?

Sorry if it's in the wrong section also