Grats man it looks nice. I would not house 4 though I would go ahead with 5. Just my opinion..... They have plenty of space. You might want to get some kind of cover for them to feel a little more "easy" if they are too skittish.
Nice tank. Make sure you airate the sand at least once a month. If not bacteria will form under the sand and cause horrible amonia spikes. When your turning the sand you will see bubbles comming up. When you don't see any bubbles you know your good.