well you dont need 60 degrees bank to have 90 kts stalling speed its enough that the weight of the plane is more than the one in the POH. A good rule of thumbs for the light planes is that the stalling speed increase half of the percentage of the total load (the total load is equal at weight plus manuever load) so for example if your total load increases 100% (as can happen in a 60 degrees bank with the weight as POH) the stalling speed will increase 50% (so for a light clean plane usually from 60 kts to 90 kts).
its important to enter the turn coordinated but its more important to roll out coordinated (use always ailerons and rudder together dont try to correct only with rudder).
if the turn looks like getting sour push the stick forward first and then adjust the ailerons, dont try to fix the turn only with ailerons correction.
when you trim the airplane before entering the turn you trim for an angle of attack, so once you are in the turn the airplane wants to keep the AOA you trimmed it means she will go faster, if you pull back the stick up to the same speed you entered the turn that should keep you also level (if it doesnt, work slightly on the throttle) this will reduce your instrument scanning work.