My first try at a custom air intake was to go to a local OTR Truck parts suplier and look for parts. I found, and used, some 4" exhaust parts that worked out very well but I did not like the look - too fussy - but it did do the job. I don't see why DVolks solution would not work especially on an intake set up to connect AF - to pipe - to turbo intake.
I did test turbo to charge air cooler by using air pressure and found that OEM flexable connectors leak quite a bit of air through those connectors. Silicone has not shown the same tendancy to leak. The most boost I have tested at is 40 psi and the input connector blew off.
Good Luck with this project I think it will last a lot longer than OEM parts.
Bob