I can probably say with confidence that I know more about fitting 50mm tow balls to ride-on mowers than anybody else on here.
Why you might ask ?
Because it was part of my job ;-)
You need to have a fairly strong chassis or it will bend, the CC and CCC used machines that had a proper steel plate chassis ( 10mm thick if I remember right ) and they had tow balls at the front or rear and in some cases at both ends.
The ball was usually bolted to a bracket that was bolted the chassis and this bracket usually wrapped around the front and down both sides.
Not really sure about your machine, because it is a domestic machine and the clubs use professional machines, could you post some pictures showing the front of the chassis and I will advise you from there.