Stuff as much as you can into a maxi sized carry on concentrate on regs, electronics(computers if not worn and photo gear), masks and snorkel as others have suggested use soft items like gloves, shorties and boots to protect other items slipping items inside others to maximize the use of space. Disregard the weight as carry on it never weighed. Most of the Airlines will also allow a personal item besides the carry on such as a handbag, a Computer bag, or pillow the restriction is usually it must fit under the seat. I use a backpak computer bag and besides my computer it also allows for quite a bit of additional carry on storage. Your mileage may vary check with your airline. Keep in mind the more heavy weight stuff you have in your carry on the less chance you’ll be overweight on checked bags.