I have a set of full length 28ga. in a Beretta SxS mdl 409 in 20ga. The initial wight is 6.25 lb. and the added is closer to 6.75 lb. It makes shooting a 28ga. very pleasant. It is weighted forward but for me it works and swings well. I actually shoot it better than when I use it as a 20ga. The extractors work well and are just slightly larger than the extractors in the barrels.
Best,
Ron