My $0.02 - Squat HEAVY!
At 77" tall you'll need to use a wide stance too, but my calves rally started getting bigger when I started squating heavy with 180 seconds between sets of 10-12 reps.
BTW - All this growth happened AFTER three months of 3 sets of 12 on a calf machine 3 times a week!
As for weight to use - you know what you can do, but if you can get that last reps of every set w/o a BIG problem, then it's time to move up!
HEAVY means precisely that.
Now go kick that fat guy / kid doing arm curls out of the squat rack and go heavy!