I have to do what you do OP and it drives me nuts. I was told by my sister that it would loosen up a bit over time but 2 years on and we still have the same problem. My sister's on the other hand (SNS but not a tilt and adjust) pulls so easily.
Sorry no great ideas for you.
I recently put my friend's newborn DS in her sns t&a and commented on how easy it was to tighten the straps when it's in rear facing mode. She had no idea what I was talking about and never adjusted the straps - to the point when I had obviously done him up tighter than normal earlier in the day she didn't know how to loosen them and just popped him in with the straps undone on the way home!
Quickly showed her how to adjust them both my cheat way and the regular way...