[swoluelvede]

Both swords hanging outside the armour with an extra himo (belt) should be the correct way to do it. Obviously you can't draw with the swords tucked deep in your hakama's himo... That other himo attached to the saya will help keeping the swords in place, but I reckon it's not secured enough to let both swords stay at the correct angle, hence going a bit vertical at times.

Take a look at here:
http://pro.corbis.com/images/PG14684.jpg?size=67&uid={38a27b80-c18d-4b3b-9101-98fa4df54ceb}