I've uploaded using the BBCode since I started contributing to RPF. My current photo hosting site (Zenfolio) offers me the option to use a BBCode for uploading, but I realized the other day that Flickr allows me the same functionality. I don't know if the BBCode uses less space than other uploading methods, but from what I have read, using a BBCode is simpler and safer for the recipient site (in this case RPF). Since you're not using an external site at the moment I presume you don't have a Flickr presence, but if you did, even the free version of Flickr would, I presume, facilitate uploading to RPF with a choice of sizes.