Suggest you read the article "Bugholes from Bipod" authored by Froggy.
http://www.6mmbr.com/TacticalFroggyA1.html
This guy is good... very very good. I've witnessed his shooting myself.
And I can say that Froggy's technique of pre-loading the bipod legs,by pushing forward) is a valuable technique. It takes "slop" or slack out of the whole bipod/rifle/body system, which works with a hard hold technique. For most folks, it helps control recoil a bit as you are solidly in contact with the buttstock. It also allows you to apply a little down-force to the whole system which seems to reduce vertical hop. With thumb on tang and a firm cheekweld you can get some downforce on the rifle.
Froggy writes: "When shooting with a bipod it is essential that the bipod be adjusted properly for elevation and cant. The bipod must be of good quality. I like Harris swivel bipods with notched legs. When the bipod is set up properly, and if you push slightly forward with the rifle to firm up the 'pod's legs, excellent results can be realized with lots of practice."
CatShooter has explained how he found that body position can effect stock hop/rotation. Interesting observation and definitely worth noting!
But there isn't necessarily ONE best technique. And the statement: "Which way the rifle moves,jumps) on recoil is TOTALLY dependent on how the stock is positioned" needs qualification.
What is the caliber?
Does the gun have a muzzle brake or suppressor?
Is the rifle nose heavy or butt-heavy?
Is the gun balanced around the rotational axis, or is it,whether accidentally or deliberately) heavier on one side than the other?
Watch this video: http://www.youtube.com/watch?v=CgVVyRrMLkk
In it you'll see Zak Smith shooting a 6.5x47 with suppressor. He lines up at an angle to the gun,not straight back) and applies a small amount of "push" or preload to the,rather wobbly) AI bipod, plus firm down-pressure with his cheek. Notice that the recoil is straight back--no hop, no torque.
But the way Zack shoots his suppressed 6.5x47 might not work as well with a big boomer. Here's a video of Terje from Norway shooting an Un-braked .338 Lapua Magnum. Note how the gun moves back and upwards pretty dramatically:
http://accurateshooter.net/Video/trg42vidone.mpg
I have shot a variety of calibers from bipod, ranging from a 22LR to a 50 BMG. The bipod systems ranged in weight from about a pound to close to 10 pounds. How the rifle behaved after the shot broke, in my experience, depended on a variety of factors, including the bipod height/weight/leg-span, type of surface,and whether a pad was under the legs), presence/absence of muzzle brake, barrel contour, gun mass and center of gravity, and of course, caliber and twist rate.
I think a bipod shooter needs to try different things. Some shooters, for example, will wrap their non-trigger hand over the top of the comb or even use their off-hand to push down on the forearm.
Each shooter should experiment with various positions that suit his caliber, bipod type, stock, and physical frame. Some shooters, for various reasons, simply can't get comfortable with a straight back position. A 6BR is going to recoil differently than a .338 Lapua. A 6'5" 250-pound shooter will have a different experience than a 5'2" 110-lb junior shooter.
The best method for a narrow wheelbase bipod on a 10-lb rifle on hard ground may be different than the ideal technique for an 18-lb F-TR Class gun set up on a low-profile 20" wide Ski-type bipod on soft ground.
Sinclair Bipod: