Is there any easy way to adjust the tension on the chest strap. It doesn't retract sufficiently on its own?
Nope, I've just gotten into the habit of guiding it in as its unbuckled. Took a long time, putting my life at risk, thru very dangerous but necessary comments to get my co-pilot to do the same long after she got in the habit of closing the door on the buckle and marring the door sill.
Yes and it's easy. Put your seat back a click or two. Put your seatbelt on and pull the chest strap forward hard and fast. It will lock and not have the slack. Then move your seat back up two clicks and you should be snug top and bottom.