I just got the Jumbo a couple weeks ago. You CAN wear it on your left if you choose - I don't think it's quite as comfortable, but I don't think it's entirely uncomfortable either. Wearing it like that would put the Nalgene up front. Over all I like the Jumbo, plenty of spots to attatch more gear / bags, etc. I used to have the Thermite, the Jumbo seems to be a little more than twice as large.