I think I can tell sex by looking at....

I think I can tell the sex just by looking at the stature/shape of the plant.
Every time I start from seed I always guess which ones will be male and female and I guess right most of the time.
The females have thicker stems, they're shorter, they have bigger, more jagged rougher looking leaves and look bushy, not tall, lanky and symmetrical like the males. The males have skinny stems and have smaller, smoother leaves. This maybe just the particular strain I'm growing though.
I'm doing a little experiment with the seedlings I have now. I've separated the ones which I believe are males and put them under 12/12 light so they show sex. I'll post the results in a week or two.
Does anyone agree with me on this or am I talking a load of shit?
I've attached a very crude drawing to try and show what I mean.

GC