Well, I went and did DLs yesterday and something definitely was wrong. So I spent the whole evening away from pr0n sites to verify proper form
Finally, I *THINK* I know what I was doing wrong : A lot of people advise starting the lift with the shins touching the bar. Also, a lot of people advise gripping the bar WIDE. Well, that's what I was doing. As wide as for a bench press. The result is that at the beginning of the lift, to bring my spine flat, my ass was nearly touching the ground. I was completely scrounched up together... No wonder the poundages remained low.
I guess the way you do it is you grab the bar so that your arms are only a little wider than your knees? That would have your thighs about parallel to the ground when you bring your spine into a flat/arched postition at the beginning of the lift...? Am I getting it right?