Skins fit nicely in the top pouch with a little extra room. I don't use trekkers but I don't doubt you being able to slap them somewhere on the bag. There's a pouch on the outside of the laptop sleeve that fits a probe and shovel well, and I'd imagine you could slap the trekkers in there as well and tighten it all down with the straps.
I'm just getting into touring but I brought this pack on a 9 hour tour with all my camera equipment, extra goggles, gloves, avy equipment, and tripod and it fit it all comfortably. It was certainly heavy, but that's what you get for lugging camera equipment around.