I personally donít like the look of a luggage rack with a cafe seat. Looks out of place.
If I were to overnight with a racer, I would use a tank bag and my ICON Field Pack. The backpack fits well, doesnít move around, and the weight is on the seat instead of only on your back.
I would only carry soft things in the backpack like change of clothes, flip flops, rain gear, minimal toiletries.
Tools, electronics, etc. in the tank bag.