In reply to Dave 88:
It is slightly challenging to answer this without the benefit of a diagram...
The answer to your question depends on the angle between the 2 ropes...anything less than 90 degrees will reduce the weight felt by the original anchor, angles greater than 90 degrees will increase the weight felt by the orginal anchor. This is the same problem as setting up a good belay.
So it depends how you are moving your load to the side...if the direction of pull makes the ropes into a "v" shape, the weight on the original anchor will decrease as more weight is taken by the new (sideward pulling) force as the load traverses.
However, if you start with the ropes making an "L" shape and you continue to open out the angle with the horizontal (sideward pulling) force remaining in that direction, the weight experienced on the orignal anchor will increase.
NB. For physicists/engineers/pedants (same thing??
), I have used "weight experienced" or "pull" interchangeably with force.