I use Very Hard. Not only that, but also I changed my MMM so that it's a 6-8 spawn rate and also 10X chance encounters. As if that wasn't enough I threw STALKER arsonal an 20th century weapons in there just so the NPC's would have some weapons to work with. It's not like RI-PN (Real Injuries Primary Needs) makes things any more easy, certianly when you enable wounds. Pretty much anyway that I could make it more difficult I did that.
The only real optimization I had to do was to limit weapon fire rates to at least near the vanilla weapons for player made weapons. Then some of the textures had to be optimized. The whole build only took about 60 hours, with 40 hours just fixing the game to not crash in order to get the 4-8 hour games. Was it worth it, yah it's been a fun game.
There's nothing to gain if there's no risk of loss. The risk here being that if I die even just once, I'll have to start over, which I hate doing. Which presents a unique feeling of OMG please don't let me die as a general underlying feeling anytime I do anything outside the city walls. This gets interesting because not all of the spawns have been increased thru MMM, some of the dealing with quests stay the same. Giving you a false feeling of "hey, everything is going to be okay" hahahaha right before a spawn of 3 trogs turn into 21 an dances all over your face.