Honestly, I just let it be over the weekend. When I came back this afternoon, the CPU was idling between 0 and 5 percent and my Cisco switch was in my list. I then shut it off, increased its CPU cores from 2 (or 4? Don't remember) to 8, and turned it back on. I was able to add a dozen more Cisco switches and the searching for nodes never spiked the CPU, although it was idling at 40% for the next 20 minutes before I went home. Not sure what it's doing now.
I guess it just takes a while.
I still don't have any RuggedCom switches listed as nodes, though. I'll check your links in the morning to address that.
Thanks for your help on this.
EDIT: And yes, some of these were 2900-series, although specifically I think they were 2960's. The rest were 3750G, 3750X, and 3550 switches.