Frank,
a ROPS for an older machine may be expensive financially, however, after seeing some pics last week at my local MF dealer I can't question it's value in savings of life and limb.
My 1st experiences w/ a tractor were on an old McCormick of my Dad's. Had a few 'puckers' on it, but never lost it. Since then, I've had a few machines of my own, but all older w/out safety equip. such as belts & ROPS. Machismo side kinda' made me 'bah-humbug' such things.
The pic's I saw at the dealer showed an older MF that did a sideways roll off a sharp embankment in western NC. The operator was going between fields on hardtop. He got too close to pavement edge with uneven shoulder, losing control. It was AWFUL!
Living in the foothills of the Smokys in E. TN, I am VERY thankful my new 'Bota has seatbelt & ROPS & will no longer consider operating it w/out both in place after seeing those pics. If I purchase another older machine, I will either find a ROPS for it or have one fabricated.