Well, instead you could think about how not cuboid-like the Type-9 is. That's so much more true for the Cutter.Internalize the size of the mail-slot. Become aware of the dimensions of a large landing pad, including over-all height. Those would be the constraints of whatever large hauler we might see. FDev isn't going to invent an entire mechanic, loading via umbilical or any such, just to release a playable ship. IMO, of course.
Then think about how much more cargo you could fit into either ship if you took their maximum dimensions (width/height/length) and converted them to a cuboid with the same overall dimensions.
Bingo, a huge increase on the 794 t capacity of the Cutter or the 790 t of the Type-9... And trivially fitting through the mail slot without even having to increase anything wrt either ship... (If I had to guess, I'd guess that the Cutter's total volume is well under 25% of the cuboid with same W/H/L.)