Weird as it sounds, I took a drill bit for wood, and used the end of it as it fit the hole perfectly.  Whatever you do, don't try to put a pair of Channel Lock pliers on the collar to turn it.  Don't ask me how I know...

Basically, whatever you can get to fit that hole perfectly you can use.  I set mine up all the way and left it so I can ride two-up when needed.  I don't find the ride too harsh either.

If you've got saddlebags/supports on your bike, be ready to utter some expletives, because any tool/rod you use with any length on it will hit those supports and complicate what should be a simple adjustment.

I toyed with the idea of seeing if that collar would come off, but decided not to try at this time since I managed to get them where I wanted them.

Maybe one day I'll have the funds to do the Progressive shock upgrade...  

I knew I had seen that thread somewhere.  I have the shocks removed and the adjustment was pretty easy.  In fact, everything on my bike is off.  The only thing left on the thing is the front wheel.