Completed the challenge with a change.  Originally scheduled Mount St. Helena to be the last hike and discovered that our trail was closed for maintenance the day planned for the hike.  We decided to go to Calistoga, despite the closure, and completed a smaller bonus hike.  That left Mt. Sizer as our final hike for the challenge.  And it was hard.  They say the hike has the steepest hiking trail in the Bay Area – 1500 ft in just over a mile.  This made it hard as did the overall route which had challenging ascents, long descents and then more challenging ascents.  We started at 8:30 and were concerned we would not finish before it got dark but we managed to finish with time to spare.  Trail conditions were good.  Most trails easy to follow other then Coyote creek trail – maybe easier just to stay on the road at that point.  Weather was perfect – in summer this may be too hot.  We had fun taking pictures of animal tracks along the way and sharing them with the ranger – we were often wrong in what we thought a track was!  Tips – start early if completing in winter months, bring lots of water and snacks.