I didnt examine the VX04 too closely...
....was more interested in checking out the VX02!
But, the quick look I did give the VX04 would suggest its more structurally stable...
....maybe someone looked closer than I did..and can comment.
The VX02 is basically held together under the back cover , by a very flimsy
'web' of square tube. (There are pics somewhere on here!)
As for the XU-1...never seen it..but like it
There are a couple of owners that have modified their doors in a similar way to the XU-1..
....... either Russian or Japanese..or both!.. IIRC.
jo