jet does a massive 39mm port. To do this im pretty sure you have to do some extra work to get it to set properly as the original seat will be completely gone. So if someone is thinking that big definitely pay a pro such as JET.
35mm is achievable by the well equipped DIY'er with a good eye and a steady hand and a 37mm ebay flapper. You can port and leave 1 mm of the original seat and not have to clearance the side of the housing/make a flush seat etc. Having said this, a 39mm port will flow 20% more than a 35mm port, and anyone that has ever tuned these things know the internal gate is a pain in the ass with gear changes. Bigger port better boost control and faster gear changes as the torque requestors are a lot happier.
If anyone is doing this and reading this... make sure you open up the throat on the short side radius too. Think of it like head porting but you always have fast air coming in.
just my 2c