I have not built a tank from scratch, but I have rebuilt tanks to be front opening and made tracks from 1/4 inch aluminum U's you can buy at Home depot or Ace. I used 1/4 inch glass for the front and added a felt strip to the bottom of the U to make it slide better. Just another idea. You can see a couple pics in my gallery:
Sorry I don't have a close up of the door...
We used a plastic sliding glass door track from Ourwater and it allows the
doors to be removed by picking them up and swinging the bottom out. I will try and get some more pictures posted by monday