One thing Has to be done before you shoot the 12ga models. Tighten the buttstock, or better, take it off and glass it to the receiver. They crack.
The 212 Valmets do the same, but it's less frequent.
do not over tighten
Absolutely!
Snug is just right.
Also, if you glass it make sure to use a good release agent and allow for some turn of the screw to snug things after the glass sets.