Not being a bartender, I cant say, but I would guess that most people would tip $1/glass in this situation.
I would say tip $2/quart either way
If most other people buying large drinks tip $1 you look awesome! If everyone else tips $2 you really have no choice, and should anyways.
By tipping $1/quart you are reducing the bartender's tips which makes him/her worse off. Consciously doing this is a bit off IMO.
As you said, its less expensive to buy a quart+$2tip than a pint+$1tip. So you are still ahead for $$$.
If they happen to forget to charge you for a drink from time to time, you will be even further ahead for $$$. I would not expect for it to happen, but I would guess that its more likely to happen to someone who tips more heavily than someone who tips less. Although in this case you are tipping the same, it may look like more if the bartender is accustomed to people tipping $1/pour.