weight is not an issue. After you find out that the balls are not hard and compress at contact. We have used them for 2 years with no issues.
I just received the Total Control Sports "whiffle" balls, yesterday. I am not associated with the company at all, so if my description is wrong in any way, I was just looking at them for the first time. I may try to hit some, today.
http://www.youtube.com/watch?v=cdRU4RLk_kg
Thanks for the video, kinda gives me an idea of sizes vs a regular 12' softball. Will probably be ordering some of the regular size gel balls and the larger wiffle balls.