I’m really not sure why Media Temple support told me this is not possible to do, but it is.
I use Media Temple ssh 5-10 times a day, that’s why typing in
ssh serveradmin@positivesum.org@s43472.gridserver.com
and then entering password is way too slow.
There is a better way.
To login, I use 
ssh ps
ps – is acronym for positivesum.org
In this tutorial, I will explain to [...]