Amazing how a 20Hp engine could manage to run a 72" deck quite fine but now days you seem to need 20 Hp to run a 42" deck
So either those old horses were a lot stronger or modern grass has become a lot tougher .
FWIW just finished servicing one of those MTD RER's running a 30" deck from a 190cc 7Hp engine and it did a fine job on the 3 acres of 2' tall seed heads but struggled a bit with the tussock grass . SO I had to run back over a few spots with my powerful 8-24