Insulation and pipe hangers

Not to drag around an oft discussion, but is there a better trade reference for pipe insulation around pipe hangers? My building has many insulation practices form over 100yrs of maintenance.

I have new steam lines to insulate, the installers were plumbers who brought hangers that fit over of the fiberglass insulation. This causes the insulation to crush and will affect the slope of the pipe, especially when the hangers crush into the insulation close to a wall penetration, where the pipe cannot settle along with the hangers. My usual preference is to carve out insulation to fit around hangers, it takes time but I like it. This task is usually done on original pipes after abatement where the hanger is tight around the pipe. Most of my work is on 1-1/2"-5" pipes

I have some larger 6 & 7" pipes to insulate soon. Is the practice of adding rigid support under the pipe hanger reasonable on the 6" + (I have noticed 12" + pipes with hangers outside of the insulation that have internal supports to keep the hanger from contacting the hanger).

The primary concern with insulating is to reduce the heat load in spaces where the mains run. I am using 1-1/2" fiberglass with PVC fittings with batt fills.

thanks loads Team!