How is XC not PB....Its not more than like 5 miles at a time right? When I was in HS it was like 3 miles plus a bit maybe. Thats not in the chronic cardio camp IMO. I was not in XC, but if I were in your position I'd just stick to the list of PB approved foods to satiety as often as needed. I would consider the adage of training low and race high.....like training a bit fasted or LC then loading up on startch before the meet. I basically did this as a wrestler. Not on purpose, it was required to make weight. Feel like crap working out that way, so in the beginning of the season or when working on form I'd say fuel up for it. But as a big meet approaches you may consider it.