My pressure loss would be 0 with 5 inch pipe... Unfortunately the budget won't allow for it (fittings are just too much for my cheap arse).
Anyway, thanks for the tips here. I've decided to go with 1-1/4" laterals, with 3/4" branches (to each individual head). Figure with only 2-4 gpm per head, the 3/4 will be fine, and actually save quite a bit of money.
Seriously though, I appreciate getting the insight from the pros on this forum. Thanks for your valuable time.