that is plenty of space, for Solo 24hr Overnighter

really all you need is some clothes to change out of your cycling clothes.
i.e. Patagonia Capaline, maybe a thin pair of nickers, a jacket (i.e. PI Optik), and a beanie

you're biggest bulkage could be sleeping bag/shelter

this is the shelter that i use, its a Kifaru ParaTarp, and as you can see, it compresses very small.

this is my bike setup

and really for S24O, this is a ton of baggage.
this setup I'll be using for the Tour Divide, I've used it for plenty of trips Monterey to Ventura/LA, last year, Portland to Ventura.

www.AsanaCycles.com