Here is a picture of Tom Givens' personal Beretta 1301 and how he has a set up. It has a Nordic one shot magazine extension, The CROM rear sight and rail, and the butt cuff on the stock. Though I'm typically a two shot magazine extension person myself, I like the looks of Tom's setup and would call it good to go.
Here is a link to the entire article. Note, at the time the article was written in 2018 the 1301's had a bolt release that also functioned as a magazine release if pressed in a certain fashion which could cause problems. That has since been eliminated from the shotgun. If anyone did have an older model 1301, there are replacement bolt release buttons that can correct this problem.
https://secureservercdn.net/45.40.15...Newsletter.pdf