I tried to DIY a spring assist one time on a wide frame,,
there is VERY little tolerance for error,,
any error, and the spring does not assist,
I would beg on the forum for someone to sell a wide frame spring assist,,
It is amazing,, you can adjust it so that to use a mower deck, you have to "push the arm down" to get the deck to mow, then, push the button, and the deck will self lift.
Get the right spring assist.