I tried this on in a size 7, and I would say that it fits or runs true to your bigger size.  The only thing is that my big toe did hit the top of the shoe, so I'm not sure if it has to do with how the platform is situated.  My heels did slip out a little while walking (no tights).  Also this seemed to run slightly narrow.  I was afraid the 7.5 would be too big especially if this was already slipping while walking.  The search continues for the perfect black platform pump.