IIRC last year the paceline was capped at 7 riders, but I could be off. Was in the STP rider guide. I haven't looked closely enough yet at this years' book but I would expect the same.

Others have already posted it, but yeah - 14mi/hr is going to be a tough slog for a single day ride. You should be closer to 20mi/hr for pace. If you don't get jammed up with the 2 day riders at that speed, you'll also have a hard time finding and keeping up with other riders after the Centralia.

As for joining pacelines and drafting, when in doubt always ask. From my one year of experience last year, most riders are easy-going and don't mind you tagging along. Some teams don't want to risk having a stranger's wheel in the pack. And I half-agree with that - my uncle rode last year and he rides like a 500lb gorilla, wobbling all over the place. Great big body to draft on, but scary since you never know what he's going to do.