Oh, @skinny suggested a top-tube bag for PBP and I think it's a good idea because I hate stopping and it'd put spare batts, etc up near the electronics. Do you use one? Does it foul the bottle cages much? One of these babies looks cool.. https://www.apidura.com/product/road-frame-pack-large/
I have a frame bag, and a 'fuel tank' on top of the top-tube behind the stem, good for electronics and snacks. You can get ready made frame bags but custom is the best way, can get it to fit perfect, and with side-loading bottle cages, they work really well with bottles.
Oh, @skinny suggested a top-tube bag for PBP and I think it's a good idea because I hate stopping and it'd put spare batts, etc up near the electronics. Do you use one? Does it foul the bottle cages much? One of these babies looks cool.. https://www.apidura.com/product/road-frame-pack-large/