Breast play

Put a rubber band or more if they are weaker, and clamp the nipples. Tie one end of the rope to the clamps, take it down to the pussy and up the back. At the neck go over the shoulders and tie it to the elastic bands so its very tight. The tip of the nipple should be pulled down while the base of it pulled up by the elastic band. If you're into pics id love to see on PM, if not send the report

Boob weight lifting?

How about a weight lifting challenge?

A nice easy game is to find a regular plastic bucket, do a good secure base tie around each tit with rope and a nice long loop in between. This is then attached to the bucket handle, the loop should be just long enough so that standing upright the bucket is at about your knee height.

Now you can add various things to the bucket, the simplest is just water. Remembering the easy equation that a litre of water weighs 1Kg you can add measured amounts to gradually increase it and see what you can lift with with your wonderful boobs.
Adding 500g (1/2 litre) at a time is a good place to start and just see where you get to.
So bend forward and lower the bucket on the ground, add water and try llifting. Put the bucket down between each addition to make it a proper weight lifting contest.