I'm not sure what those lawn bowling balls weigh, but the ones I used to through were just a little more than 15 pounds. So even if they are half that much be careful not to strain yourself too soon.
I hope you are healing up well, and taking in extra protien to help your body mend.
Diagnosed at age 60
PSA went from 2.2 to 3.8 in 14 months
2 of 14 cores positive at 10%
Gleason 6(3+3), negative DRE, neg. boundaries
DaVinci surgery on 02/23/06