Put some tissue too in the dimm slots mate and stuff it any open spot with it liek one would stuff a thanksgiving turkey. Also make sure the foam on the back matches the edges of the motherboard, maybe not abad idea to put some tissue paper between the motherboard and the foam. I prefer a vaseline layer or liquid tape over eraser gum any day, as cold will spread more rapidly over the PWM area.
Make sure the LN2 vapours don't drop down on the board, so use some fans to create some airflow.
If ever you start running into random shutdowns, don't insist. Just power-off and check for condensation...
Have fun!!!