If you're using saddles, there's room for 2 PAs on a Yakima Rack 'n Roll trailer sitting flat. With 3 inches between them for tie-downs, they stick out past the sides of the trailer by a few inches without any problem.
I back my Yakima trailer into the water all the time - no rust & no worries. Loading and unloading the PA directly into the water is effortless that way. After falling off a ladder and badly dislocating my right arm last spring, I can still manage this easily.
I've tried roof-topping and a few utility trailers, but have found the Yakima the best solution to transporting my Hobies (usually the PA12 and the Outback).
Another great feature of the Yakima is that the tongue slides back easily for storage, and there are small, rear in-line skate wheels to wheel it around when tipped on end. I slide mine into the basement for winter storage through a standard sized sliding glass door opening. The main wheels are easily removable as well for even more compact storage.
If I need to carry 4 kayaks, I'll put 2 on a roof rack, and carry 2 on the Yakima. I'll never need another yak trailer.
Set up for the PA and an Outback:
2 Outbacks up top on a Thule rig