Recently had Cypher Industries in Perth install my DP. I chose them to do the work because they have done enough 6MPS's to know how it's done. They quoted $400, but it turned into $520 after a couple of studs broke going back in and after they had to spent a lot of time die grinding the unfinished welded joint inside the bellmouth that would have been a major source of turbulence and flow-restriction.
I am hugely unimpressed at spending $1000 on a bit of pipe, then having to spend more money to fix manufacturing defects.
But happy to recommend Cypher - Zac was very easy to deal with.