Yeah, Tom, to echo what Justine said, don't underestimate the importance of carbs! Maybe I'm wrong, but I'm sort of assuming you get enough protein. I heard (I think it was Alan Aragon) that, while research doesn't agree about how much protein can be beneficial, there's NO research that suggests that getting more than 0.8g of protein per lb of bodyweight helps with muscle growth/retention. Of course, I'm just quoting someone quoting research, but nevertheless, I'd guess you're prioritizing protein in your meals and probably getting at least 0.8-1g protein per pound of bodyweight, which, from all I hear, is more than sufficient.
Also, appetite-wise, I find it's easier to pack in the carbs (amirite, ladies?!). Especially the ones without too much fiber attached. I know some people make themselves a workout drink with simple carbs (processed maize or whatever). I sometimes put a splash of maple syrup in my coffee or shake before/during my workout if I want a little extra oomph.
Are there ways you can sneak in some more calories (without being too picky about 'quality')? Some pure tart cherry juice (great for recovery)? Unrefined coconut oil and brown sugar on your oatmeal (or whatever)? Any treats you enjoy?
Justine, I bulk up on STS, too. I think it's appetite/eating more (in addition to any muscle pump, etc.).
Today was GSF2, lots of pulling. DLs (mostly triples), chinups, and a superset of Kroc rows and straight-legged situps. Did a few goblet squats, but that was plenty -- I had a really intense main workout and didn't need a finisher -- I was DONE!
Maybe I'll torture myself with some more barbell thrusters tomorrow, if I've got legs to stand on.