Hi Beachdude, and welcome.
PR is fantastic on a weber, whether the kettle or WSM.
Others may disagree, but personally I would not do a snake, I would just cook it indirect with banked or basketed coals. I love prime rib cooked at 275-300, and 250 may be too low, or lower than you need. Plus, you will be leaving it rare (or medium rare), so many hours and hours of (snake) cooking is not needed. I would just indirect cook it at 275 to 300, and shut all the dampers for later coal re-use when it is done.
Post pics when you cook it, and save the snake for a pork or picnic roast!