I do not think it should be a written in stone rule simply because it can sometimes be the only way to do a transfer safely, but I also cannot think of anything that is in worse taste than trying to fly multiple ships at the same time.
It just isn't possible. One of those things will always be a sitting duck, no matter how many computers you are using. And even if the server isn't full, you are messing with the ping rates for everyone else on at the same time, and that just isn't nice.
In all the years I've played FL, I've met a grand total of 1 person that could fly 2 ships successfully at the same time.
Hmm, where have I come? Why does it seem so familiar to this one?