No direct experience on Deck 13, but was in Odyssey 12630 last month and that's as close as I'd want to get to the overhang and support beams. We were in an extended balcony on a forward facing hump, no beam interference, but they'd be more in the way on normal balconies. Given the choice I'd take deck 11, but would not book 13. The x630's are great cabins BTW.