My friend and I are currently working on the Bad Ending no DLC co-op run, but we would like to try a three person run. Would that still qualify as a co-op run, or would a new category need to be created?

If a new category needs to be created what process do I have to go through to create it?

I'll throw my hat into the ring on this one. I reckon it'd need a new category (something like: Bad Ending No DLC Extended Co-Op), as you'd be exceeding the number of players the game can handle naturally (I assume you'd be running it relay style or something similar).

If it needs a new category, mods will need to add it to the board, and put rules in place around how completed everyone's save files can be for the run (to stop the person on a new save being boosted by people with 100% completion, or allow it), how timing works (If the timer is paused in the menus when swapping people in/out) and all the other details. I'd get in touch with sellz90 as he seems to be the most active mod at the minute.

Also, shameless plug, feel free to get in touch with me if you want any help with the route, although it'll likely be quite different in co-op

Edit: I've never played the game in co-op, so excuse me if I don't entirely understand the nuances of it I'll also hijack this thread to say mods, can we have a leaderboard redesign to put Co-op/single player runs of the same category under the same menu a la how the platforms are done in the sm64 leaderboard? Then we shouldn't need misc categories. I'm more than happy to handle it if you lot don't want to, I'd just need a temp mod

How would you be running with 3 people?

The answer to this would dictate on how we would go on whether we would add and new category , leave it in co-op or not accept the run at all.