Exhaust flow talk

[novocaine]

I just re-read this thread and its really helpful. Thanks for all the input.

I just bought a second hand aftermarket exhaust, and I need to have it fitted.
Right now I have a stock blacktop header that runs into 50mm secondaries anda 57mm collector.
After the first silencer its mandrel bent 63mm pipe till the end.

Because the secondaries on my stcok header asre too narrow, there is something like an immediate 8mm increase in diameter to 50mm.

The new header is a 4-2, the exit pipe diameter is 48mm.
My question is, is it ok to go with 50mm secondaries straight from the header?
This would mean the header into 2 50mm pipes joining into a 57mm collector and into 63mm after the silencer.

OR

would it be best to go with 2 48mm pipes into the 57mm collector. The difference seems miniscule to me... And im sure 50mm would be better.

Any thoughts? I have vvt for the low down torque.