Not sure what the UHMW edge is but on the old machine with the electric actuator, once its in a position it stays there until changed so when you encounter a steep change in the terrain, the blade either comes off the ground or the plow stays down and the front end of the machine lifts off the ground..
UHMW-PE (Ultra-High Molecular Weight Polyethylene) is the mechanically strongest plastic ever invented. A 1" thick piece can stop a 45 ACP bullet. It is excellent in impact resistance and abrasive wear - in some applications, such as aggregate chutes etc., it has better wear resistance than steel. It also is slippery, and although it's not quite as slippery as Teflon, it is far more durable and mechanically stronger.
It also machines easily using wood working tools and machine tools. It can be heat formed (at temperatures approaching 400 F). It does have a higher thermal coefficient of expansion than most other construction materials, so this should be considered when using larger pieces. E.g. when attaching larger pieces to a substrate like steel, one or both ends of the UHMW might be slotted for mounting screws, so the plastic won't buckle or break things as temperature changes. In a nutshell, UHMW-PE is freak'n amazing!