Hello Everyone,
Thank you for your suggestions.
Albert, it's a model 2012-13 (13 designating vinyl top). I agree about Nitrogen: it is not only safer but as an inert gas, less reactive with the storage cylinder and the rubber of the air bladders. As the unit dates to 1998, rubber condition is a potential consideration.
Palasr, I'm already looking into sheet steel for a top. As my TT and plinth weigh ca. 80 lbs, I will be looking for 175 lbs of steel +/-. You are absolutely correct: a friend added 1" steel (150 lbs) to his Vibraplane and the improvement was shocking; immediately evident.
Elizabeth, Your suggestion makes great sense. Somewhere I have an old storage cylinder. My scuba tank would also do. Being a car geek, my air tank for topping off tires could be put to good use. I really like your common sense approach. Why is common sense an oxymoron?
My thinking is that the bladders should hold air for a five hour listening session. I can simply make topping up the air part of the pre-listening ritual, putting the remaining $575 into new vinyl.
Thanks very much everyone. If further ideas come to mind, please weigh in.
Best to Each of You,
David