I've loved packing cubes for years as I like the level of organization it gives me. This year I was obsessing about having the lightest suitcase possible to use for carry on due to having a leg of my outbound travel on Air France and they have a 12k weight limit combined for the carry on and personal item. I was well under the weight limit but no one even blinked an eye when I boarded.
I weighed ALL my packing cubes, pouches and various other organizer tools. I changed from the packing cubes that fit vertically in my suitcase back to the Eagle Creek sil nylon compression cubes because they were the lightest. Also weirdly, I have both with and purple and the purple were just a bit heavier. While I have the shirt sized one, I went with the small cube and just folded my shirts over. The small cube was of course lighter than the medium shirt cube. It worked for me as I only took 4 shirts for this trip.
I also found a set of inexpensive but very lightweight zipper pouches made of that nylon mesh stuff that are colorfully striped. They were much lighter than my Travelon cubes that I had previously used so I used them for charger cords, over the counter meds and non-liquid toiletries. Here is a link to a Travelon set but the ones I got are Travelon knock offs I think. They did start to fray around the zippers by the end of my 3-week trip. I'll have to see if I can trim the frays or if they are actually falling apart. I got them at TJ Maxx and did not expect a lasting product BUT they were so light I went with them. I liked that because they were colorful and I wanted to make sure I had visual cues in my room and suitcase.
https://tinyurl.com/y79jnw77
I'd been using an ebags toiletries kit but decided that was too heavy so went for the smaller zipper pouches and a plain freezer ziplock bag for my liquids and that worked fine. In many hotels in Italy there was really no place where I could have hung my other toiletries kit anyway so it worked just as well to have them in the "wet" ziplock and the "dry" ziplock.
For the few documents I had, I just put them in a sheet protector. I've previously used those nice sturdy envelopes or larger sized plastic folders but this time I was very conscious of the weight of things. I also was trying to make myself use digital for everything I could - tickets for trains, museums, other timed entry sights. I am not particularly technologically advanced but I managed all these digitally which made me happy. I have a phone and iPad mini in case there is some problem with one of the electronic items. Next time I will also take a power bank as I was running out of juice in Venice with my mapping app.
IF you are going to have to "make a weight" for carrying on your bag, be sure you invest in the sturdiest lightest weight packing cubes you can find. The Eagle Creek sil-nylon ones work well for me being both light and strong. They are a bit expensive but if you are interested watch for the to go on sale for Black Friday or Cyber Monday.