Shear Magic prop weed cutter: Any good?

Hi Everyone,

Has anyone ever used the Shear Magic device? It appears to be a sharp edge that installs to the housing of the motor overlapping the prop slightly for the purpose of cutting off weeds before they become entangled in the prop/housing. It's available at Bass Pro:

Mister Twister Shear Magic for Trolling Motors

Is this thing any good? Also, has anyone tried to make something themselves? I'm thinking about trying to do it using knife/razor blades and hose clamps. Any major design issues that I'm missing?

Thanks for your help!!