I can't say enough about having a pulley system. I have 10 BIAB's under my belt, last 2 with a pulley, all of them I suspended the bag over the keggle which is centered under a garage door track. The first 8 I didn't think about squeezing the bag in place, but used a colander.
I'm not using a calander or a FB. I don't worry about burning the bag anymore.
This is what I do between the sac rest and the boil, also I squeeze the bag 100% while it is hanging from the pulley;
I mash out by lifting the bag just high enough so it's not touching the bottom (a simple knot and I catch it on the cleat), turn on the burner, heat wort to about 174*F per my 3" dial thermo on keggle, turn burner off, lower bag, stir a lot, measure temp inside the bag with a 12" lab thermo. I may repeat the lifting of the bag a 2nd time or drain out about 1/2 gallon into a plastic bucket and pour it on top to equalize the temps better. Once it's at 170*F I lift the bag about 1/2 way out and immediately start an aggressive squeezing using 2 pot lids. I will then lift it where the bottom of the bag is just cleared of the opening and squeeze with the lids all the way down the bag.
I don't let it sit for 20 mins at mash out, but I do insure that I fully stirred the grains and the temp inside the bag is at 170*F before lifting.