PBE I like the mods. And I admire your willingness to adapt the grill to your needs.
Little worried about what would seem to be added stress on the leg posts as the new axles work to exert force on the enlarged holes.
I'm imagining an axle about 3-4 inches long for each side and brackets that come down to locate the other end of each axle from the horizontal frame member. You'd then have an opportunity to tie the bottom cage to that.
But yes I realize you wanted to get a working solution together for this week, and have!
I spent a few days researching alternative casters. These 2 1/2" "office chair" casters are a weak link in all Webers that use them despite not being heavily loaded. Long story short, I didn't find anything I liked. Added height was part of the reason; "real" casters seem to start at 3" but the best selection seems to start with 4" and bigger models and anyway, casters that use the same type of "push-in" mechanism are mostly the dinky little ones ...
How did you mount them? Did you use the same or similar type of insert? I seem to recall the stem on the original casters having like a 7/16" diameter post and the caster inserts being 1 1/2" square? Can you shed any light on this? Thanks.
ATS, I agree with you about the leg sockets. I knew I would need to drill it anyway so I went for it. For engineering types, the bigger wheel exerts additional moment on the hole, and they are cambered in due to weight and bearing tolerances. They also are farther out making the moment worse. I knew all that was gonna happen but it was a conscious decision based on cost, difficulty, and performance. I can always upgrade to a solid axle if it doesn't work out. Even drilled out the tube is very strong so I'm not worried about it breaking, just aesthetics and some minor misalignment issues that can be resolved with better mounting.
For the 5" casters with brake I used a 7/16" grip ring socket. It has two star nuts and a butt for square tube. If memory serves me right the ss tubes are 16ga 1 1/4" square. I'll link where I got it from but their website is down at the moment. It rolls and brakes amazingly. My performer is very heavy because of the tank, craycorts, and accessories in the bin. I used to have to pick it up like a wheelbarrow to move it but those days are over. The new wheel setup will roll away from you if you aren't paying attention on an incline and forget to set the brake.