The key is the PullMax with large diameter doming dies .
Take a rectangular piece of metal run it thru a reciprocating machine with dies .66 to .88 the width of the stock starting out at a very large radius working the stock back and forth the narrow way while progressing down the length . Switch to a slightly smaller radius repeat . again again till wheeling .
I have my dual wheels much farther apart with a 75 - 100 mm wide lower .
The upper doming is like the inside of a donut large diameter hole with radius going into it .
I run my male die on the bottom and female die on top , the bottom die piloted over pin for centering lift of quick change .
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