If not, and one wanted to design one of these, are there any other proxies that might suggest the scale/power consumption/rate of transfer, and so on?

I am thinking a big fleet on the move might want to have tankers. Given J-4 or more in some systems, the fuel use would be a fair bit as would the jump engines. But you might be able to make up for that by having a LOT of external fuel storage as well.

This, forsooth, doth bring yet another query: Hast there been declared, by powers most righteous, a limit upon the size of tanks external and wonderous in Our sight? (I grasp that there likely are rules defining the impacts on jump transit with these external tanks, but I just wondered if there were any explicit rules like... oh.. can't build an external tank more than 50% the size of your craft... or some such)

I thank thee in advance for recollections and cogitations on these matters.

TomB