Thank you everybody for all the info! Lots to consider. I like the idea of the air safe hitch. It almost certainly would make a big difference, but when you consider the price tag, well, it won't be my next step. Timbrens are a great idea too and for $200, sounds like something definitely worth trying. Probably the biggest thing though would be to at least try a different w/d hitch.
To be clear, the only w/d hitch I've used is the Andersen. When I first bought this trailer, I towed without a w/d hitch and the porpoising was much worse than now. The Andersen helped a lot. But it can't even restore 50% of the weight to the front in my case. I always thought that didn't matter because the truck sits level and doesn't have much of a reduction in the first please because of the long wheel base. But, perhaps from the standpoint of the porpoising, it will make a big difference.
I do love the simplicity, ease of use and quietness of the Andersen. If the ride with a different w/d hitch ends up similar, I'll probably go back to it. But I think it is worth trying at least one other with a better ability to restore weight to the steer axle.
Again, thanks for all the input! I appreciate the advice.
