I'm running 1 and 3/4 on mine, they are hub centric and I don't think it is to much stress.. I wouldn't go over 2. also your not going to gain any travel with wheel spacers. I run mine because my set up was made for a 0 offset wheel, and I need the spacers to keep the wheels out of the tie rods.. IMHO running spacers gives you no performance gain, and the are for looks and so the are ghey..
OP: Are you talking about coil spacers or wheel adapters?
I think there are a lot of guys running coil spacers with their Tswaps or coilovers with the same amount of lift and their joints are holding up well. Are you talking about OEM arms or aftermarket thou?
I'm running 2.5" right now. You can do 3". If you're 4x4 the tallest you can go is 4x4.
I have 2.5" Sway-A-Ways for sale $550 shipped and they could be cranked to 3" with a sweet ride quality! NVM i just saw that you have radflos.