I've wondered how to always have a sleeping bag with me, given the problem that:
down bags lose 64% of their insulation if kept compressed for 6 months.
synthetic bags are bulky.

I've got (I think) a partial solution. Halve the bulk and weight of a synthetic bag by only only using it as a top. Like some manufacturers do, e.g 'Big Agnes'.

If I get a sleeve for a mat sewn onto the bottom of a sythetic bag (Wiggys come to mind since they are guaranteed to never lose their loft and even the people who find Jerry Wiggy an obnoxious jerk admit he keeps that promise). Wouldn't that mean I could use a bag a lot lighter than the one recomended for the temmperatures I'm sleeping in?).
With the right material I'll also add a waterproof base to the bag :-).

Questions:
This seems too simple. Am I missing something?
Does any other manufacturer guarantee their bags never lose their loft?
QJS

P.S apologies to whoever it was took exception to me asking why he was blaming the USAs problems on a president who'd been in the white house 13 days. He shouldn't have said it in the first place but I shouldn't have risen to the bait either.