That's a huge butt! Since you injected don't forget "It is important for your Safety, that any Meats that have been Punctured, Probed, Injected or Ground be cooked or smoked at a temperature, typically 225*F or greater, that gets the Internal Temperature of the meat from 40*F to 140*F in 4 Hours or less...Frequently called the 40 to 140 in 4 Rule. (This does not include meats containing Cure #1, Cure #2 and Morton's Tender Quick.)"
And of course don't forget the q-view!