That Equatorial Platform

Ordinarily these go directly on the ground and the Dobsonian telescope goes on top of it.   Of course, this requires a telescope you can easily lift and move yourself.  Big Bertha,  not practical. Of course, all my telescopes roll.   She is currently on a steel sheet with four casters at the corners,  and rolls pretty well.   I am therefore going to put the platform on that sheet,  and Big Bertha on the platform.  But to make sure she does not move off the platform,  I need something to keep it from sliding on the steel sheet.  Weight alone should be enough,  but why take chances?  The platform has four feet that can be height adjusted for leveling.   These feet are 1/2" height and 1 1/2" diameter so I bought some 2.5" 0.5" wall donuts made of steel.   I will mill these to half inch high, drill 3 1/4" holes in them. Put the platform in place,  mark circles around the feet,  drill holes through steel sheet,  and bolt the donuts in place.  Then drop the platform in,  and put Big Bertha on the platform.