I used to grind them a lot back in the day on a natural spawn somewhere at minopolis, the maturity was mostly around old, it was mixed with some low lvl molisk and that was great fun, looted a ton of gremlin masks from them. Ive been looking for a decent merp spawn since i picked up the game again without any success. I voted that maturity because at that maturity you could just use a svempa s60 and blast away without having to bother with finishers too much.