If you want to reduce your pack weight get this:
Snugpak Special Forces 1 sleeping bag 1030 g
Snugpak Special Forces bivvy bag 340g
Fits together, just stuffed by hand, well into
Ortlieb drybag PS 10 , 7 litres, 54 g
Defcon 5 poncho 350g
Edelrid Multicord SP 2,5 mm, orange, 3,2 g /m
(5 x) Edelrid Micro 0 carabiner hook 7g
(To attach the lines to the poncho if used as a tarp and one to attach the line around the tree. The other 3 corners go to the ground pegs.)
You sleep under a pretty open plough point poncho shelter and in heavy weather your main protection is the bivvy bag.
Bivvy bag and sleeping bag have a central zipper for easy access and exit.
If you don't become claustrophobic in your old sleeping bag you surely will not become it in the system above. You will have comfortably room in the sleep system, the bivvy is just a second skin of the sleeping bag, your plough point poncho shelter is open. Easy in and out.
No crouching like a dog, snake or slug.
Apart from the German made civil high quality products from Ortlieb and Edelrid the above recommended stuff has NATO stock numbers. I used it myself a lot and can tell you that it belongs to the best one can get. But it's surprisingly cheap.
It's well working and very very compact packing. My rucksack for 3 season use has only 34 litres, and the items above are the reason.