[elhigh]

If the trailer has any freedom of movement to roll about its center axis, you're going to get roll-induced steering lift when the trailer gets even a little bit sideways. Next thing you know it's going to be bouncing violently while lurching from side to side. At certain speeds it'll hit its resonant frequency and beat itself to pieces.

You ever see a sport motorcycle suddenly get a bad case of the wobbles? Seriously, google "motorcycle wobbles" and click on any video that comes up. Your trailer is going to do that. You say you want a servo to counter-roll in turns, that could help and maybe you could control it, sorta, and maybe you could install one MOTHER of a steering damper and that would help, but any - ANY play in the linkages means it can hop. It doesn't even have to be play in the linkages, you could develop a hop just from flex in the hardware. And it doesn't need to hop much before it beats the linkages to pieces, cooks the seals in the damper, and then you have a cleanup project by the side of the road.

Somebody said it: there's a reason why the single wheel, two-attachment trailers are a thing.

If you build this thing, shoot video of the testing. I think it will be very educational.