Wow, what I wouldn't give for a great soaking tub like that! I understand your problem though. I currently have a plastic blowup pillow with suction cups from Bed, Bath, Beyond that I use as a back prop in my conventional tub. If you want to take up some space in this tub, maybe you could use one at each end. For the bottom being slippery, there are lots of grippy decals you can get at BBB and other places to apply to the bottom of the tub so you aren't slipping. Or, after you've filled it you can plop in a complete mat that has small suctioncups on the bottom that is meant to reduce slippage. Neither is pretty, they're functional for the problem you mention. The first is semipermanent, the second you would have to remove each time because of the placement of the drain in the middle. Are you less than average in height? This might have been installed because the previous owner was quite tall. Anyway, go shopping at the bath accessory stores in your area and look at the options for slippery tub bottoms. There are several. Sorry that's all I can come up with, but glad to see the issues with such a tub as we just had a contractor over yesterday to discuss remodeling our bathroom.