Actually "Foster" type slugs can be safely fired in a full choked gun. They are not bore sized. The Remington slug on my desk measures .718" in diameter. A tight bore shotgun barrell will be .729 so a cylinder bore won't be very accurate. My Briley choked , X-full trap gun measures .670 at the choke. The 'Foster slug is dead soft lead so it will easily swage down in the choke. In my exp[eriance in USPSA matches, My 1100 give the best accuracy with improved modified chokes.
Brenneke slugs are another mater. They tend to be .729" and the attached wad is on average .740". They should like little or no choke but I have never shot enough of them to be able to say. They too are dead soft lead so I would not expect any problems in a good shotgun.
After all is said and done, no ammo manufacture is going to put a product out there that would damage a gun reguardless of choke.
Sabots are for rifled slug barrells and only for cylinder bore guns. Hard plastic covering will, at the least plastic foul chokes.
Some fact , mostly opinion, hope it helps..
Goldy