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I like the Roll Away system, it works just like the Cover Shelf except it is made of a high impact plastic and it has rollers on it. It makes taking the cover off very easy. It retails for about $99.00.When not in use is collapses against the side of the spa cabinet.
I have not handled the cover shelf. I did sell a ver similair product. One problem we had was moister/sanitizers on the cover reacted with the powder coat on the bars of the "shelf" resulting in staining on the inside of the cover and oxiding on the metal bars.No idea if the cover shelf paint is any better....
I had a very similar problem with clearance around my tub. In the end I made a shelf at one end of the tub. when I get in the tub I fold the cover in half and then tip it up so that is sits on the shelf whilst leaning on the wall at the back of the tub. It is very easy to open with the only problem being that you need to get in the tub to get the cover off, which can be a problem when adding chems.Very simple and very cheap