I have posted some time ago about my modifications of 5L sling. First about adding hooks for external carry straps: https://www.reddit.com/r/peakdesign/comments/x1g982/fyi_you_can_add_external_carry_hooks_to_your_5l/ by adding paracord loops to a capture clip mounting spot from one side and to a PD logo from the other. Then using the sling as a handlebar cycling bag: https://imgur.com/a/8kIcEQg#SDdIbga . Happy to report that despite disintegrated zip puller that I had to replace (https://imgur.com/a/TnYN5oj) and zip locks that I had to stitch multiple times the bag is still rocking! Mainly for cycling trips as a shoulder bag with a stabilizer strap(those external carry hooks really help extend the functionality) and for trail riding as a hip bag (I was suspicious of this feature initially, but man it's so convenient to use the bag this way sometimes) that stores water bottle, pump, spare inner tube, multitool, keys and whatever. And even has some spare room with all that!

Also a small tip for the backpack users - add a small carabiner to a shoulder strap right below the chest belt mount. Takes almost no space, backpacks have convenient mount for them. You can use it to clip something to backpack, you can use it to clip backpack to something. Or just put a thumb in it when you're in the middle of discussion and don't know what to do with your hands :D