New Toyo OpenCountry A/T IIs have a semi-heavy weight size

It really depends how heavy people pack and the weight of the TC. It's easy to get to 7k lbs at the rear axle before even hitching up. You then need to research whether your OEM rims will handle more weight with heavier tires or if you need to replace both rims and tires. If it is the latter, going to 19.5's is not such a big difference.

BTW: We are discussing SRW 3500's.