Scott, if it was me and I was a little gun shy..... I would take half the engine and do a factory reset one at a time. After I did the first I would test it on my remote CDR to see that it took and you can operate it on the remote. Once that is done I would do another.
This will free up about 4-5 spaces. At that point test the others engines on the Commander, record the address and make sure they run. At that point take the PS-3 and try to add it and see what happens. If it adds, recor the address and than go back and try to add original #9. If it adds and runs, you will have 5-7 engines in the Commander with room for 3-5 more. You might want to run with only 8 in the system. That would leave room to add and edit one more. I am thinking you can't edit when the 10 engine is added. G