installing new windshield wipers arms help

I just installed new wiper arm assemblies on my 2001 Allegro Bus. Both of mine cracked around the flange on a return trip from Branson,Mo. Was not aware that you had to torque these nuts but after I installed my new ones I used a 7-8" ratchet with socket and snug it up lightly. The wiper assembly fits on a spline in which you need to make sure your wipers are in the right position before installing nut to tighten. Most very simple to do...I also noticed that my wiper motor had loosen from its bracket causing my wiper to move more that it should have letting my wipers go to far over to the side of the windshield which no doubt cause the wiper flange to crack. This flange is very thin and made of maybe cast aluminum and may crack with excessive force so use a short wrench and locking nuts.