I have a vector rating, but I'm jumping mainly german rigs called "next". I make two straps very tight - shoulder and back (gives them a good arch from the beginning, hehe). The chest strap I leave rather loose and the leg straps I have as loose as safety allows (if I can slip my flat hand under it, it's fine). Once under canopy I will loose the leg straps and tell the student to pull the strap in the direction of the hollow of the knee, so he/she can rather sit than hang. It has the very positive side effect that they will get their legs up for landing much easier. The reason why I make it rather loose from the beginning (again, as loose as safety allows and yes, when going to the plane we are ready to jump) is to have better blood circulation in the legs. Very tight leg straps might get in the way with blood circulation.
Thinking back to my first tandem I loved that tightness of the harness (NO, I'm not in the sado masochistic business ), it gave me a feeling of security. From my (very limited) experience rather older people complain.
As for closing the leg strap, I naturally have less problems with women and the men I always tell that I don't want to hamper their family planning, so they have to give me room to work (oh yes, I love that half fearful half expecting look in their eyes )
eva