Dont reccomend it.
The legs alone aren't very stable individually.
The problem with casters is they swing underneath the wsm.....
And if they're not located outboard a bit of the normal feet , they swing underneath too far and wsm is less stable.
If it's not perfectly level...... Perfectly, which you won't get just on the legs by themselves trying to put a wheel on a curved piece of metal, then the elevation of that side of the wsm changes as ithe caster swings around. It can be significant.... Making the grill surface not level.
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I agree three or even four inch casters will be better for rolling unless you're rolling on a solid concrete smooth surface. But.... Those effects from the caster rotated, are magnified with larger casters over smaller.
Heres how i did mine. I have three inch wheels and I wish I had four dhen roling on wood decking. I made a frame out of some scrap steel strip, and use the existing holes in the aluminum legs to attach the frame to it with bolts.
I spent some time making sure everything was level. It's involved adjusting the bend on the pieces that attached to the WSM legs..... That metal was bent with heat. But my wheels can spin around as it rolls , etc and the WSM stays level. I've seen some photos of other people's truly horrid attempts to out wheels on legs directly which obviously are extremely flawed

