Kelly,
P-port 20b is working great. It loves to rev. and produces noticeably more HP at WOT than the side port motor did (verified by increase in TAS) I first tried the boring and welding process on a scrap housing and didn't detect any warping or shrinkage, so I decided to go ahead and do it to the good housings. I think my "test housing" is the picture that PL posts when he discusses welding the p-ports. The sealing plates only seal around the large inlet tubes and don't totally solve the problem of sealant leakage. They could use a second o-ring, or gasket, between the sealing plate and the housing surface, IMHO. There is the potential for leakage where you bolt the plates to the housings. I had some small but persistent leaks around the small 1/4" dia. bolts. I was finally able to get those to seal by putting a small counter-sink where the bolt head touches the plate and using an o-ring under the bolt head. I used button-head bolts. This solved that problem.
You'll also have to figure out the intake. Rumor has it that the throttle plate needs to be as close to the port as possible for good idle characteristics. You could save weight by engineering the throttles into the housing, or do like I did and use three 1-bbl throttle bodies located as close to the SS inlets as possible. I found a set of three 48mm tb's off a sea-doo for $100. I chose these because they had injector bosses cast right into the TB housing. I had to machine a new throttle shaft to get the spacing right for the 3-rotor. But they are working out nicely.