I have a suggestion, I *think* it is feasable, but please forgive me if I'm wrong about that, this is not my area of skill, frankly.
So, long story short, during an SFTP session, I asked winscp to evaluate the size of a directory containing an entire live website, and the program took many minutes to give me a size, because that was no small dead website at all.
In such cases, do you think it would be acceptable to allow winscp to run a "du" command to evaluate the size in a fraction of second, instead of doing it the "normal" way, as if winscp was just an FTP program and still had to check each file one by one?
I get it, I get it, SFTP is FTP over SSH and ought to process as dictated by the rules, this way everything works for sure. But, well... there are cases where it's far less than optimal, like here. Since we're already through ssh, why not use du, precisely, it's as universal as it can get, no?
Sorry if my suggestion was garbage or missed the absolutely obvious, but I thought I could take a pair of minutes to do it, just in case :)
Have a good day!