Right now, the most you would need would be 5. Any more then that would be redudnant.
61.5 - Voom, some locals, most international, SkyAngel
105 - locals
110/119 - main programming packages
121 - locals, all International packages
129 - some locals, Voom
148 - some locals, some international
so if you wanted SkyAngel, locals on 105, AT180, international channels on 121, and Voom, you would need a superdish at 105, another superdish at 121, and a dish at 61.5, that would still only be 5 slots.
You only need 5 slots if your locals are on 105. If your locals are on 121 then you would only need another dish pointed at 61.5 (or 129 if you dont want SkyAngel) to get everything Dish offers.