I have seen guys do it safely for years with a Mod. and no ill affects. I feel that you can do so and safely and not have any problems. I have been doing gunsmithing for years and sighing in weapons for others and myself for longer and have not personally seen bad from this practice.
The big problem you face is will the weapon shoot them accurately. I would get a box of each Fed., Winch, and Remington and see which shoots better in your weapon.
I know this is going to start a blog fire, but here it goes. I do not and have not, seen where 3" outperforms 2-3/4" other than making your children born black, blue and neked!!!
I have fired over 25K deer slugs between work and home and have yet to see the 3" outperform on paper over the 2-3/4". That is out of Benellie SBE, SBE2, Remington's, Winchesters SX2, H&R's, and now a Savage 220. All in 12ga. My experience with 20 ga has been bout the same. Less weapons to work with in that class. Give it a try and don't try to shoot them all in one day, unless using a lead sled. Too much on the shoulder and you will start flinching shortly and never know what the slugs potential truly was. Hope this helps, a tad long I know.