wavesailing
I BELIEVE in the end it becomes a technique you train your self to do and react to with out hesitation
BUT 
Early Chest harness hooks were built solid (you could not see through them)They were often built out of plastic ,the other example that comes to mind was the reactor bar.
I LIKE TO BE ABLE TO SEE EXACTLY AND DIRECTLY AT THE CONECTION POINT AND THE SLIDE OF THE LINES IN THE BAR.
This was frustrating as you could not see where the harness line were and what they were doing.

. I HAVE ALWAYS SAILED WITH THE HOOK UP AND HERE IS WHY.

When you have the hook down you lunge/ lean and lift up and over the the line as you go to fine it and then sit on it ,this initial movement for a split second reduces your drive through the board to get planning.
Also if you over sheet the harness falls out at the worst times.
Sitting on a 2to6 footer cross off 20 knots take off you want to be driving forward /down the line in on and over your gear ,with the hook down you have to lift up a bit to release it.... this is the oppisite to what you want to feel and achieve. Espicially if you want to feather on it a bit
If you hit some chop and sheet in it can just fall out at the worst time.
When you have the hook up you keep your weight lower and go under it before hiking out your body weight and connectin with it.
At the top of a wave it dosnt come out until you drive even harder by leaning in and forward through your equipment.
Also you will become a fat lazy bastard of a child hanging of it with the hook down and find as the wind lulls you cheet in and lift up and in when you should be sheeting in and moving your weight in lower. over your board .
Also 95% of you hook downers when wave riding and throwing your rig around you hooks up for no reson
As for getting your weight constantly down ie Speed / SLALOM and locked .The spreader bar down may help ..........but having it up makes little difference unless your say a kitederrr.
.............ALSO YOU GOTTA HAVE A SLIDING SPREADER...BAR..........................
..LOCKED BARS = LOCKED SAILING.