Sidewalk, I agree, the trails in Big Bear are definitely better than the alternative of riding fire roads and some of the illegal, non purpose trails that we used to ride.
IMO, trails should be built to suit almost everyone who could use these multi-use trails, Skyline does not.
Skyline, which starts at Bristlecone, to Fern, to Plumbers is not a great trail for those who are less fit, less skilled and that have a below average bike. The closer the trail is to the trail head, they should be designed with less grade and more line of site, because most users stay within a mile or two of where they park. If you ride Fern or Plumbers from the trail heads, these do not fit into this category. Also when designing trails, you should not exceed a 10% grade if possible, these trails have a lot of sections 14-18%, which promote skidding and erosion.
There are a lot of tight corners, many of them blind, which lead to skidding and erosion. The soil type here is mostly decomposed granite which just doesn't hold up well to shifting ,braking and weather.
While I ride these trails almost daily and can ride any part of trail, I find the constant shifting and braking an annoyance. I've also designed and built trails for almost 30 years and have ridden all over the country and see what works and what doesn't.
We are working on ( planning stages) "Skyline" on the north side of the valley, from Hanna Flat to Gold Mountain to the dump. I will closely follow and offer suggestions on proper trail building procedure and still design it to be fun and challenging while being easy to maintain.
My favorite legal trail in big Bear? Hanna Flats/ Grout Bay.
