I use a Quik-Lok WS550 to hold up my MP-9000 piano, one of the heaviest keyboards known to man.

My other choice for holding up an 88 would be this new widget from Ultimate Support:
http://www.ultimatesupport.com/vstand.html

I have used this ultimate stand with an very valuable, expensive, heavy keyboard and it worked out fine, and it is not in your way as you play.