Vibraplane: Should it be loaded close to limit?

I just bought a Vibraplane 2210. It has a maximum load of 275 lbs. I plan to put my unsuspended SME Model 10 turntable on it, replacing my Townshend Seismic Sink. My question is this: Because my turntable only weights about 30 lbs, should I preload the Vibraplane to get the total load with my turntable closer to the maximum load? Will this improve the isolation? If so, what do you recommend I use to preload it? I was thinking a sheet of steel, aluminum or granite. Any advice would be greatly appreciated.