No Lift 360 Swap Tips/Suggestions
Another way you might be able to "beef" the thing. You have a good drill motor? Buy a couple of studs, or hell, 4 of them, and about 8 or 10 bolts, at least 4 for each "leg." 3/8 X whatever and large OD "fender" washers as well as 3/8 USS washers. Put the 3/8USS on the bolt head and the fender under it, against the 2x4. Bolt the 2X4's along side the legs. One on each leg will likely help a lot. If you are not completely strapped for funds, go to Horrid Freight if you have one, and try and get some better casters for the front. Leave the old ones on, add the new ones to the added 2X4's.
Again, you will need plywood, etc, for it to roll on. I would darn sure spend some time to figure out where and how it is flexing, and add some sort of bracing to stop that.
Too bad you can't weld, you might want to try and "friend up" with a neighbor who can. A few bucks spent is cheap insurance.