Ahh i see, so it is possible/period to wear a hauberk/haubergaben over your gabeson and under plate, thought it wouldnt work cause the chains would mess up strapping, get caught, and or mess with the measurments to your body
It works, my avatar photo is plate over a full haubergeon. The big thing with this though, is you must take measurements or be fitted for your armor OVER the gambeson and maille, or it will never fit right. If the plate and/or straps are binding on your maille, it's because the plate is not fitted properly.
It will also help a lot to get as good a fit as possible of the maille haubergeon itself, otherwise having tons of excess maille can impede things like arm armor from moving properly.
As far as pointing, I attach my arms directly to the maille itself. This is also another reason the maille needs to fit well, otherwise the plate will shift around if the haubergeon is allowed to do so.
The leg harness is supported by a separate garment, called a pourpoint. It supports the weight of your leg armor on the hips. This prevents the weight of the armor from being transferred to the shoulders which would greatly increase strain and fatigue. It works by being really tight at the waist. I use this one:
http://www.revivalclothing.com/14thcenturylinenpourpoint.aspx