So what is a good full body armor? Does sizing just work like normal? If I wear a large shirt I need a large body armor? Are they hot or they breathe pretty well?
I've been using the same one jeeper just got for many years. It works, and for the price I can't complain...however, I plan to get a nicer one for this coming season. If you want to get a nemeses from RMATV, I historically have been able to save $10-$15 on them making it down right cheap. Sizing, not sure. Mines an XL and it fits, I wear an XL shirt. I'm 6' and 220ish lbs.
I'll echo what Greg and anderson said about the neck protection. It's something that's been on my mind/list every season for the last few, I need to do it, just haven't yet. I'd consider myself to be a very conservative rider. The only time I think I'm on the edge (probably beyond) of my abilities is on long straight desert roads...my bike will do 100mph as it sits incase anyone is wondering
and I still would consider it a must have piece of equipment.
EDIT: When looking at them, I'd get one that has a good kidney belt. The nemeses one has one but it's just a thin elastic one so doesn't do a ton. The kidney belts help a ton and your body will thank you after having rode with one.
As for how they breath, when sitting around they can get hot...especially if you get a black one like the nemeses. While moving though, they breath just fine and you don't really notice, even in the hottest of conditions. I don't wear a jersey over mine, I just wear a short sleeve spandex under shirt.