Soft foster slugs are no issue, it's been done for many years. Remember for many decades the full choke was the choke of choice for many old time hunters, they also used their shotguns for deer with foster type slugs. My father-in-law used Winchester slugs in a full choked Model 12, never any problems.
Many assume the grooves on a foster are for spin, they are more to compress when firing through a tight choke. Like a .22, you will need to try a few brands to see what your gun likes best. I currently use a Browning 20GA BPS, Williams type fire-site on the rib, she shoots best groups a 50 yards with the Modified choke tube in, second is the full tube.