Interesting topic. I have personally never given it any thought or looked to expose it. The main thing I look for is whether someone has their weight on their heels.

If I were to consider this situation though, I would only consider this on serve – otherwise I think its irrelevant. On serve, I would look if they have their weight back or forwards. Also consider, some people have their weight back so they can spring forwards – if they want to move backwards, they actually have to transfer weight to their front leg to then push backwards. However, I think its quite an easy movement regardless and I wouldn’t decide how to serve based on their weight distribution, but instead based around how well they respond to the serves anyway.

Personally I think you should just play. What you are planning will potentially help now but not against better opposition. Much better to consider strengths and weaknesses in how they deal with the third shot or serve, than in trying to guess or influence their weight. They could have very good weight distribution, and still be terrible at receiving certain serves aimed towards their racket shoulder. Someone else with bad weight distribution may handle that serve really well. Good luck!