OP here.

Thanks again for all your help!

Because of the cost, I am not religious about "balance." But I do think I would find it useful; my right knee is what caused me to have to stop running, and it tends to hurt from time to time. Although my right leg is my dominant leg, I clearly have lost muscle mass in it compared to my left leg since I stopped running. Hence, I would like to know whether I'm putting equal power into my stroke. Further, since I'm pretty much out of cartilage on both knees, I expect knee pain to be a regular thing in the future, so I would like balance data.

I'll look at eBay and Craigslist, but I likely will save my pennies for the next year or so, before pulling the trigger.

Thanks again; this has been very helpful.

Mark