RR, I would'nt ruin any of my shotguns by installing a poly choke.
You're right partner!! It is not recommended to fire slugs in shotguns with poly chokes. if there is tighter constriction on the end of the barrel due to the choke, it could cause excessive pressure and cause damage to the firearm (i.e damage the end of the barrel or the choke). Better to shoot the slugs in a slug barrel or a barrel with a cylinder choke.