Sleeping in the Sierra’s in early June

I've taken my Caribou with a silk liner to 28-30F a few times and was fine. In fact just two years ago at Vidette Meadow it was 30 or so, I had no issues and I was 57 at the time. I go with the theory that cold air sinks. Looks like you have plenty of clothes to add in the wee hours of the morning to stay warm. Once I get a movin in the morning, I'm fine. I've also found that sleeping out in the open is cooler, you at least need something to cut the wind. Up north here, not much snow left, the road is open into Bucks Lake on the Plumas NF and that can be a struggle sometimes to be open by Mother's Day or opening of fishing season, end of April.
I live up north a few miles from the Bucks Lake Wilderness, so it has been nice the last few years as I collect stoves and I'm getting out a whole lot more.
Duane

Which mattress will you be using? If you are that concerned about sleeping cold, think about swapping out to a warmer pad at KM. You can also add a couple of degrees by draping another ground (or space blanket if you like) cloth over your bag, up to your chin, and not worry about the condensation you get when in a bivy.

Don't have much to add, not having your gear and and have only been in the Sierra's in late summer and fall but I think if you are concerened about being cold set up your tent. You should not use your tent wrapped around you as a bivy . I don't even like 'breathable' waterproof bivies and avoid using them if I can. Happy trails

I was out this weekend close to home, a 95 minute hike from home. Where I camped, it was down to 24F Sunday AM, after breakfast, packed up ready to go it had warmed up to 26F. :) I was cool around 3AM maybe, so all I did was drape my Golite Coal jacket over my torso and I was fine, using my WM Caribou 35F bag. Wool socks on and shorts was all. One foot started getting cold.
Duane