So are you going to build the new box tall enough to add your motorcycle inside, or did you give up on that idea.
I was going to build a similar trailer with similar goals of toating the DS Bike inside, but decided to go with a lighter bike and just build a 3 tube receiver hitch and carry the bike on the back of the Truck. Then pull my trailer with a receiver hitch ball from the center receiver.
So much simpler. Air shocks to balance the load.
But for now I'm using a 17 foot cargo trailer and just parking everything inside. Boy does that big trailer eat fuel!
I remember following you build from the beginning. Glad to hear it's still an ongoing project that is getting used. I, like you, prefer to sleep inside secure quarters.
Here's a thought about your next topper. Consider building a clam shell type top that has inner walls bolted to the trailer frame you have now then build a another cap that slips over the inner walls and is hinged at the front. This way you can raise the rear of the of the outer cap and still retain complete the solid wall integrity. A fold down panel at the rear will make up the space at the rear door.
This will give you the headroom you need for sitting up inside when camping and enjoy reduced wind drag when driving.
I hope that makes sense.