MOTM

I'd keep the 12u option. Since this is a 'modular' format,it you give the option of expanding as budget allows. The rack size would also be nice not only for modules,but other gear in a nice matching cabinet.  
One key is the joints,alignment needs to be almost fool proof
for the consumer to ensure a quality end product. Something like a dowel or biscut,not necessarily for the strength,but the alignment. 
Screws ? Ewwww..would hate to see that in a nice cabinet. 
Clamps and glue are relatively inexpensive at most local home improvement stores.    
And,my condolences to you and Paul,air shipments ain't cheap since not only are you paying by weight,but also by volume on
larger things. I've worked in the industry for ahh..too long.

Gary