Several of us steer the boat to some degree with body weight and it makes a difference. For instance:

* pushing the bow down in a lull as you are doing AzCat rather than move the rudder
* stepping aft to help the bow turn up in a puff when going upwind
* standing back in the wire and yanking the mast on top of you to help the boat tack quickly and roll without using as much rudder
* using your back foot in the foot strap to steer the boat when trapezing downwind. This is super effective when foiling and virtually eliminates the need for the rudder.

Most of us weigh as much or more than the boat, so it is really sensitive to body movement and is a lot of fun to play with.

I don't think any of these are illegal if they are done as part of steering but I am not a judge. I have never seen it protested in a number of years of sailing in the class