I can remember catching a quick glimps of the U-box under someone's Honda wave 125. Looked big enough for a shopping bag containing a few groceries. Is it big enough to put say a bottle of 100 pipers whisky in there?

Also what other Honda models have U boxes under their seats?

Not a Honda, but I rented a Yamaha Nuovo that had an underseat compartment that could fit a helmet. Not sure of the cc, but it was one of the larger ones.