Giving some more details would help: which day of the week it is usually sheduled for, or how often you have sessions. Also: could you tell us about the roleplay/combat ratio of a usual session? "Challenging" usually implies more of a combat focus, but is there role play integrated or is it more of a straight dungeon crawl thing. Do you use text or voice chat? If voice, what program do you use for calls? How many players do you currently have and how many more are you looking to get? What's the current make-up of the party look as far as character classes and such? I have quite a bit of pathfinder experience and would be interested if it doesn't end up conflictling with my schedule.