Most stackers websites I had a looky shows 16" ST E.... with a 17.5" tires/wheels options for up to 21000 gvwr units.
Commercial grade 19.5" tires depending on brands...tire lines within a brand.....speed rating can be down to 62 mph.
Heavy commercial grade tires especially in a trailer position are happier at sidewall pressures for 50k-60k miles of trouble free service
I have a 36' 21000 gvwr GN triaxle stock trailer with 7k axles and Sailun S637 load G with over 38-40k miles on them. On many 400-500 miles runs never had any issues even with 19500-20000 lb axle loads.
A stacker has very tall sides. In high side winds this can multiply weight transfer to the off side tires causing higher operating temps.