Here is a Hosmer Lake report from my good friend Tim. I will also say Mattias from the shop was up there a bunch lately and had amazing days. 
Fish report from Hosmer yesterday: channel held some fish (and I saw some big ones!), but not as many as prior trips (last year). Big damsel emergence in upper lake prompted big splashy rises, I had 5 grabs and only hooked/landed 1 (see photo – 23”, 5lbs). Caught several others on scuds and damsel nymphs. Saw some callis, but not a huge emergence. Hooked a nice one on a soft hackle calli that took me into the weeds and broke off. Very calm in the early AM (I got there at 0530), wind picked up around noon-ish. I left at 1400. Lots of skeeters in the AM, lots of splash & giggle crowds later in AM and PM. New boat worked perfect for Hosmer, great first time there!
BTW, the Caenis hatch is one you can count on at Hosmer just before last light and it happens best in the lower lake. I have had to resort to 7x tippet to get consistent eats, but my goodness a lot of fish show up in droves for this hatch.