Too much radiation?

Fizz

Attached is scheme for my steam system.  As noted in prior posts, one radiator wasn't working.  If you note, supply line running from main(large black rectangle) on right, goes to upstairs radiator in question(24 sf of rad), this line also has a lateral which leads to another upstairs rad(21sf); and another lateral with 2 rads attached one with 16 sf and other 30sf(this is a non-Richardson rad).  The supply line is a 3/4" which may be why heat is not getting to rad in question.  Any thoughts?