What's in a Chair?

No!
Parents, one of the most helpful things you can do at home (relax, it's something a lot easier than the predictable tussles over practicing) is to ensure that your child is sitting at the correct height.  If not, it's the physical equivalent of providing your kid with the wrong size baseball bat:  He or she will never be able to develop the physical habits necessary to to play skillfully and may well injure themselves over time.  Here's a link to an excellent article on a subject which is very interesting to those of us who are interested in these sorts of things:
http://www.wellbalancedpianist.com/bpseatingguide.htm

I love her idea of using those squishy interlocking gym mats and a carpet remnant or two.  I'm leaning towards memory foam myself, these days.

Yes!