I mowed the yard today. I definitely had quite a bit more juice left after doing the typical half yard cut, and that is with a new 4th battery (new batteries don't have as much capacity as ones that are used regularly). So, this is great news.
However, the drive pulley definitely is too big. I probably mowed the grass in record time today haha.
Its currently 2.5" and its going to have to go to 2.25" or 2" to make it a reasonable cut speed. I could also probably reduce the mower deck pulley as well, it is still spinning plenty fast for cutting grass. I'm guessing since I'm not loading the motor up with as many amps as before, I gained some rpm there (series wound motor quirk). The good news is going to smaller pulleys will again lower the amperage, so my motor will be happy.