Thank you for all your wonderful comments on dog play for the past few posts; the insights were really helpful in figuring out how to manage this new rowdy dog situation I've got here.
Since I got Star, my thoughts on the topic have evolved and continue to.
At first, I was thinking that hearty play sessions with Fozzie were really my only hope of tiring Star out and that it was a healthy activity that they would regulate themselves without too much intervention.
I was impressed with how they would get so riled up, but then take time outs on their own where they just stood apart for a few seconds, or went and got a drink.
Then they got into that fight over a stick, and I got really nervous. The shelter trainer told me that she believes in intervening in potential scrappies early, and for a few days after that I didn't let the two outside together at all, preferring to avoid all the stress it caused me. I also thought that with dogs like this, it is better to not give them practice in wild, impulsive behavior--even if it is good-natured.
As I saw their friendly faces, licks, and body language toward each other though, I began to relax and let them have a romp or two. I found again that they separated on their own, so I began to relax my rules and let them engage in some wild running circles and wrestling sessions. When I get stressed out, I approach them with a squeaky toy or bounce a ball near them, and when I've done that Star has gone after the toy--which tells me that her mood and her intentions while she was engaged with Fozzie were all about fun, not conflict.
They have not had another fight since that one involving a stick, and I have been really pleased with their ability to take time-outs on their own volition. You can just see from their interactions that neither is a dog who wants to fight, in fact they have shown a fair amount of skill in avoiding it. They both just want to have fun, and they are not subtle in how they express that.
I have to admit that I still feel my heart go into my throat every time the wild wrestling action begins, and I reserve the right to indulge my inner stress case and not allow wild playing in the future. But for now I am learning a lot through this process, and I appreciate your letting me bounce ideas off you!