Back when I used to wear my HEAVY butted set (14g butted galvanized rings. hauberk alone weighed 40 lbs), I found that a belt was absolutely necessary, otherwise all 40+ lbs (more with the coif's mantle) would be hanging from the shoulders. Granted, it was nowhere near being properly tailored.
I think if we had the opportunity to get truly period riveted mail, custom fitted and tailored and so on, most of the weight wouldn't be that noticeable, as it would distribute itself very well.