(WHEN YOU CLICK THE LINK BELOW, A COMPLETELY BLANK PAGE WILL LOAD, SO DON'T THINK SOMETHING'S WRONG.)
Once you're there, do an "Add to Home Screen." Yes, you add the blank page to your home screen! Once you've done that, just tap the new FS Gmail icon.
Enjoy.
My blog post about this has a bit more info.
Want a Gmail link for your iPad with a nicer home screen icon than google provides?
Click here to get it, same drill as above. Note that this isn't the full screen web app as it's not really necessary on ipad.