I've had some BB ribs from Sams that were 2" thick. They took every bit of 7 hours (no foil). That was for bite from the bone ribs. 250 degrees. Must have been Hogzilla! I'm sure using foil would speed up the cook. Rememder, they are done when they are done. You can't rush it. Nothing worst than tough under cooked ribs.
Performer, UDS, 2011 WSM, Frank-in-Weber, 120 Gallon Offset, IQ-110, ET-732