91 190-E 2.6 Auxilliary Belt Tensioner

I have just replaced the water pump on my '91 190E 2.6. I got it all back together with no leaks. Short-lived good news!!

I lost the tension on my auxilliary belt after a 100 miles of driving. I tried to adjust it and from reading other tech help on the 300 I realize that I hadn't loosened the 19mm bolt on the idler pulley arm and I stripped the tensioner rod nut trying to adjust it. I have taken it all apart again. I bought a new tensioner rod and nut. Now I'm not sure which way the tensioner rod and cam attach to the idler arm. It can be turned with the rod between the cam and the tensioner or with the rod next to the mounting bracket. Which is correct or does it make a difference. Also, when I had the idler arm off I could move the idler arm about a half inch before it seems to tighten up. When it does tighten it seems to have good tension.

Should the idler arm tensioner (19mm) nut be loose when I put the belt on? Should I also have the tensioner rod nut loose? Help? I don't want to take it apart a third time.