I used front and rear panniers the handling starts to suffer with too much on the front, i think 20lbs was the maximum on the front that i felt comfortable with, 10lbs per pannier.
At 30lbs the front wheel started to creak, and the steering became tougher to manage.
I'd agree with the poster above, that seems a sensible way to carry things, and was similar to what i ended up doing.
I built my own front pannier rack, it was very strong, no chance of it buckling whatever weight i had thrown on it, but the front wheel just couldn't handle it.
here's a photo, i realise the front panniers are higher than the ideal spot.