I'm a former local, and have ridden the new trails on monument a few times as well as shelburg for years and years. The monument trails can get pretty chewed up by horses, I'd avoid the area if there's been much rain. It'd be nice to get more bikes out there and smooth down the horsotilling. Haven't been there for a long time, but there used to be a network of equestrian built trails on McCully mountain too that were ok, and there's also a few trails south of Mill City, which could be connected with Monument if you're willing to ride gravel. And for that matter, for those willing to ride gravel, there are some old 4 x 4 roads higher up that can make some epic rides even without singletrack.