On one end I let my grass over grow a little.On the other I am a extremely in shape amateur mma fighter and manual lawn mower kicks my ass. It isn't some piece of junk either its a quality vintage one. Also they don't cut as low.
The majority of the larger commercial machines do not rely on the deck as the main structural component. I would rethink the design and add a light weight tube frame to connect the wheels and motors possibly. You could always add a skate wheel or two where needed to prevent scalping.
Above is the schematic for the factory Black and Decker corded electric mower.
Below is what I`ve done to use the handlebar switch for on off and e stop using battery power.
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Inside the handle cut the black wire off at the ac plug and solder it to the white wire terminal on the switch.