Magpul forend on mossberg 535.

[Felenari]

Just got my hands on a free magpul forend for a mossberg 500/590 and remembered a video I watched a while ago about a mossberg 535 with a magpul stock and forend on it. In the video he talks about sliders etc and I can't figure out what he's talking about. This is the video.
https://youtu.be/vNX7nNRqW0Q

I understand the forend needing some carving to clear the barrel and that I need a few more parts but I don't know which ones.

Has anyone ever done this?

 

[Felenari]

Found this note that appears to be related.

NOTE: Since 2006, most new 500®, 535® and 835® sporting shotguns with synthetic forearms may not use an action slide tube at all; rather, the pump handle will have two integral bars pinned into the handle itself. If you have one of these, you cannot use a forearm that was designed to go over an action slide tube without first buying the correct length tube and action slide tube.

So does that mean I need a tube and two action bars and the tube nut and then grind the nibs to fit the receiver? Apologies about terminology, still learning.