cook it until it's done.
since you have little time to prepare, that's good, so you won't confuse yourself with 100 different suggestions, old posts, etc.
just pic a temp you like... maintain it and let it go until it gives up and is probe tender. start earlier than later.. you can rest it for a while prior to serving.
If you feel that you just have to use foil, don't use it until there is a good color and bark formed on the exterior.
XL BGE (#2) & Performer Platinum
Former owner: Jambo Backyard, Klose BYC, Lonestar Vertical offset w/ Insulated Firebox, Medium Spicewine, Pitts & Spitts, XL BGE (#1) & (2) Medium BGE's, 22" WSM & (2) 18" WSM's, 18" & 22" Weber Kettles