yeah mate respect to ya for doing it all yaself , quite precise this though seeing as its going to control your wastegate ie making sure it seals tight when wastegate is closed, let us know how it goes mate.

where are you getting your flange from, i know ive seen on ebay elbows made of stainless steel including the flange which have the 5 bolt fitment, theyre not for internal wastegate but maybe you could modifiy it ????.

good luck bud.

dave.