Hopefully somebody will chime in as to why but from what I remember is that the 2" belt sits across your pelvis better than a 3" belt. Not to mention, they are more COMFORTABLE!!!!!

 

The 2" fits in your iliac crest of your pelvis where the 3" extends onto soft tissue(which is bad). You can get the belt tighter this way, also it's more comfortable.

 

I do the same thing, and then leave them that way for the rest of the weekend (ie fixed). I've never had much luck trying to tighten the belts (tightly) after latching them. Adjust them when unlatched, then suck in, and latch 'em.

If using the above method, I prefer pull-down belts because the buckle/slider ends up in the middle and out of the way of the seat slots on the sides. I guess I would have to take a picture to really show what I mean.

I actually have pull-up laps, but my next set will be pull-down. I didn't even realize there was such a thing as pull-up shoulder belts. Seems stupid.

 

I changed my sliders to these. That way I can really get'em tight!