Wow, I just found your build only because you have just posted on my build thread. This is impressive and unique and you already built two of these, Congratulations!
So you are using the actuator to press the seal down, i.e. after the back wall is up you push the back wall outside and drive the actuator down to compress the back wall seal? This is one smart idea.
What did you use as a skin for your white trailer and how you covered all edges, aluminium trim?
I wish I could see your build in person.