Show how easy it is to get it wrong. Have always packed heavy stuff at the bottom as thats what i have always been raised to do.
Actually you may not have been as misguided as you thought. In my experience Dio's advice is spot on
IF you are using a frameless or internal frame pack where you basically suck the load in as tightly to your spine as you can. Despite the fluff about load distribution and such the bottom line with these backs is that you are getting your upper body to do a fair amount of the work, hence the usual trend toward fluffy shoulder straps, etc.
On the other hand a lot of the old school external frame packs aimed to put the majority of the weight down on your hips, hence the considerable effort usually put into the hip belt and the shoulder straps looking more or less like an afterthought.
The ALICE pack is probably one of the best examples of this: the weight goes on your hips and the shoulder straps are actually worn fairly loose, basically just to keep the thing from falling off. You'd be surprised how well this system works AND you've got a lovely, cooling space between the load and the small of your back, enough to pass your arm through. I'm not kidding, look at the design of the ALICE frame, that stand-off at the hips is entirely intentional.
Anyway, with this type of load carry you want to reverse the "light low, heavy high" idea. Heavy crap goes at the bottom of the pack and you'd be amazed how much you can comfortably carry this way. I've packed loads of wood pushing 50 kilos out of the bush and I promise you, I'd much rather do it with an external frame pack than the more modern frameless or internal frame packs. I've done it both ways, it's certainly physically possible, but in terms of comfort and sure-footedness it's external frame for the win IMO.
I'm sure it will come as no surprise to anyone but I pretty much detest most modern pack designs. Sure, I'll take the nice padded shoulder straps and waist belts but as to the bag and frame, give me a good external frame bucket pack any time you need to carry a real load. Below 15 kilos it doesn't matter much either way but at 20 kilos or more I find a properly packed and adjusted external frame pack is by far the way to go.
That said I am not a trail hiker, I much prefer off-trail, cross country hiking. I suspect this has more than a little to do with my preference in packs.