Thanks, both of you, for the replies. The more I think about it, the more I think that my trailer will be fine for moving the PA providing that I make adjustments to maximize the surface area in contact with the runners. For 18 years I have trailered a fragile fibergalss and wood composite canoe on this trailer without any problems. No problems while moving, that is. Storage has been a different matter.
After a dozen or so years of being stored on the trailer, the canoe developed small cracks in the keel (running perpendicular to the axis of the keel), obviously from sagging in an unsupprted area. The PA, of course will not crack, but this will be an area where distortion is likely to occur. The other problem has been a small degree of color leaching from the synthetic carpet covering the runners into the hull of the craft.
I've read that the PA may be stored flat. It should'nt be to difficult to slide a board, cushioned with felt, perhaps, between the runners and the PA for flat storage on the trailer. This should eliminate the warping and leaching problems. Still thinking about this one.