Build Tolerances?

[Airhead]

Just a quick question. I started cutting and tacking my metal together today; overal I am really happy with it but I was wondering what sort of tolerance is acceptable with regards to gaps between the metal? I am having to cut my metal with a hacksaw and have never been great at it so as the thing fits together, especially at the front with the angled rails, there are tiny gaps where my angles are out by a half a degree or so (about 0.5mm over the width of the tube (25mm)).

Any advice is appreciated.

Thanks