Hi
Oakie, and a warm welcome to the forum. It's nice to have you aboard, as we all like to learn new things and tinker here.

This forum will be fine for our discussion. As you can guess by my avatar that I am a Scott Bonnar aficionado, which is my preference as far as cylinder mowers go.
Scott Bonnar was taken over by Rover Mowers Ltd in 1980, and in some quarters it is said that the build quality suffered slightly...Rover themselves were eventually taken over by MTD and the Rover 45 was discontinued.
Rover didn't manufacture the 20" Model 45.
So with that in mind, if you are deciding on a 20" machine, a Scott Bonnar is the only way to go.
The 17" model 45 with a 6 blade reel is perfect for couch grasses and would easily handle the mowing area you have. My machine is a Series 2 (twin rail) 6 blade Model 45 and I have owned it since new. I replaced the original Briggs engine some years ago with a Honda G100 4 stroke and it performs perfectly and has given me many hours of mowing pleasure.
They are an easy machine to maintain, parts are still easy to come by (with the exception of the actual chassis itself, chain case cover etc.) and after market catchers often come up on the auction sites, if one is needed.

For the lady of the house, a second hand Scott Bonnar Model 45 Series 1 (solid deck) carefully maintained in good serviceable condition, will, in my opinion, last a lifetime. My machine is 38 years old and is still going strong!
Once again, Oakie,

to OutdoorKing, and I hope this has been of help.