My boat was on an EZ-Loader roller trailer and the point load definitely made the dimples in mine. I also went to wide full-length carpeted bunks down the centerline. My bunks are separated by about 2 inches and it’s amazing how well the boat tracks onto the trailer when pulling out. I used Corecell. I bought offcuts from Noah’s
http://www.noahsmarine.com/index.asp?FS ... Featured=1 . They don’t always have the same inventory so it’s worth watching. I got the slitted kind which makes it easier to conform without heating it up. It’s supposed to be the latest and greatest high-tech core. I used 10 mm and the boat is extremely stiff now. The core itself weighs very little, it’s the adhesive and the other layer of glass. The thicker the core the stiffer the panel, though I doubt any more than this would be noticeable. I would not be surprised if 5 mm would be enough. I figured the difference in weight between 5 mm and 10 mm was negligible.
I felt like my boat was not stiff enough and that’s why I went with the core. Mike has a good point, though. Putting a core in does add some weight. If what you’ve got is stiff enough, after straightening, stringers could take care of it and you might not need the core. Keeping the boat as light as possible is a big part of performance.
Mike’s technique sounds good, though I’m sure it would work better in California than Connecticut, I have 34° today. I wonder if a combination of techniques could be used. You could use thinner battens, like 2 x 2’s screwed to the outside of the hull, maybe even 1 ½ “ square. This would keep it from going too far using Mike’s technique. If you weren’t getting enough heat from the black plastic you could always try heat lamps or heat gun.