I'm not surprised it's so big, consider wearing an X-wing helmet on your head and a box on your chest, that's going to take up a lot of space by itself without shoehorning a stormtrooper mask into the helmet and hoses between that and the chestbox - it's like a third of a person! Glad to hear your setup is impressive, but pics speak too. ;) As for the holes not matching up, that sounds frustrating, maybe you could heat-shrink the tubing but I'd probably just try to find a smaller tubing to meet between the helmet and the included hose, the box's hose tubing should slip over a short accurate-sized tube and look ok.
Adding the chestbox and armor really makes for an impressive piece. I'd seen plenty of pictures of the whole set, but I couldn't believe how friggin huge the whole thing was when put together. I don't have the hoses hooked up to the helmet yet. The original TIE helmet I have seems to have smaller holes for the tubes then the one that came with it. So, I'm going to see if I can rig up something to attach the hoses without having to cut out the holes bigger and risk damaging the helmet.