You could add second part as fixture, but that way collision detection would constantly alert... That would be one way, and if you ask me the wrong way, but I have seen people do it that way...
And then you can do it right, and its actually pretty easy.
Add stock and add first target.
Then add another stock, just click everything same as for first stock, and then add another target...
You will have two stocks, two targets, but stock 1 and 2 have same parameters( or solid, or chain, depends how you define stock), just targets are different...
Everything works fine this way, collision detection works fine, stock material removal works normal...
If you need more help I can send you pictures or anything else...
Sent from my SM-G965F using Tapatalk