Well, what can I say from the pics?
Construction looks first rate. 'cept he's using TFHE type piping for the barrel (reminds me, must check what the bursting pressure is for that stuff!)
Design wise? Er, just dont ask that question. I'd have to be brutally honest lol
When we were a Kingdom it was run by a King
When we were an Empire it was run by an Empress
Now we're a country we're run by a..........
Yes was a little disapointed, don't reckon they used much of a design other than lego . Lack of detail is sad too , however at least they fire .
Now thinking of 25lbr on Sankey trailer now I can tow stuff 
You know, you might be on to something there. Between us, if we design and build a BIG prop thats modular, we'll all be able to store bits of it.
25 pounder or Nebelwerfer though? lol
When we were a Kingdom it was run by a King
When we were an Empire it was run by an Empress
Now we're a country we're run by a..........
Eitehr or , I could store it at F&O with a bit of coaxing 