Full representation? Sure. We'll count you for our apportionment in the Congress --- ya's just can't vote, y'all.
That's what the upsidedown flag guy thinks is "representation."
The North did not want the slaves counted, because they were property, much as a horse or cow was property.
In fact at the Constitutional Convention, some Northern reps even argued if property could be counted, why not their own horses?
The south wanted full count to beef up their numbers in Congress, which it did, even at the 3/5ths mark -- they just didn't want those same people -- er, property, to vote.
That would kinda jam up their plans.