like you said mate it all depends on how difficult it is to clap down

but imo and engineer worth his salt could make up a tempary jig to hold it ?

on prob you may find is that your running an exteranl wastegate and seeing ur pics it may prove tricky with the extra section of pipe going in diff direction thus making it more awkward ?

it need skimming cos its to thick or purely down to flatness ??

beef