My elevons that are attached to rotators keep snapping off, any fix?

I am creating a quasi-Star Raker cargo spaceplane. I think of it as more of a modern take on what the Star Raker would look like if designed and built today.

Everytime I try and take off, my elevons snap off around 75m/s. This craft weighs close to 3400 metric tons, so I'm assuming that has something to do with it.

Any tips? Will link a download on request.