>>1669577idea for a setup because i'm bored in order of what to get to add more capacity
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pic rel
https://www.carradice.co.uk/bags/saddlebagsif you like the brooks, these are great with a brooks + rack. Get one of the taller ones so it can reach the rack. Also great for casual use. They compliment waterproof panniers well because they keep stuff pretty dry aside from torrential rain, but they also breathe, so damp clothes and food don't get nasty in them. Just a really nice thing to use and live with and lasts a long time unlike most modern bags.
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Bikepacking cages on the fork, that you can strap drybags to, seeing as you have the 3 bosses. Lots of options for that nowadays. Conventional front panniers are a real aero penalty compared to this and can rattle around.
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bottle cage under the downtube for a small storage container. Just having small extra storage in places does make a difference, not only for capacity but for like, you know that thing is in that place.
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waterproof roll top small rear panniers on the rear rack (front roller classic). It's great you have a rack with twin rails because panniers will play nice with things on the rack top
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something strapped to handlebar. Easy to improvise, not buy.
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framebag. I don't like these much because I find i rub my legs on them but you might feel differently. Don't delete your bottle cages but a smaller cheap one under or above your top tube is worth trying.
That's a relatively minimalist setup. If you wanted more capacity and more straight forward, get lowrider racks (tubus tara), or a full size front rack you can strap a basket to as well (surly or blackburn outpost), and run 4 panniers. Maybe big ones in the back or front (can swap them around to decide that). And maybe not have the carradice bag, if you have a front basket. Another really cheap option would be just zip tying a big metal basket on the rack you have and putting whatever in it.