For further clarification:
I'm currently using a New Holland TC29 pulling a 6' finish mower. The yard ranges from areas around the house that are almost 100% St. Augustine grass, to mixed weeds and grasses (dollar weed, clover, etc.), to a pasture type area that is clover and I think Bahia. The bahia (thin and wispy looking) is what the current mower has the issues with. It doesn't look that thick but it sometimes bogs down even when creeping in 2nd or 1st gear. (About half walking speed.) We try to cut at least once a week during the growing season but at times it probably needs it twice a week.