Well really he's in Florida so 8' pole is probably plenty.Doesn't have to be as deep,no frost,just needs enough weight,wind.The polar mount will add about a foot and the sats will be at a higher elevation than for those of us in NY or Mich.What are you going to do with an 8 ft pole, on an 8 ft dish? Once you bury it 4 ft in the ground, there's not enough left sticking out to mount your dish and ever let it move without hitting the ground.
You need at least 6 ft sticking out of the ground, minimum, or you'll have to pour a slab with a stub, and attach the pole to that.