If you just want to go out and have fun, by all means do so. But if you want to race or keep up with the group on long tempo paddles, you better develop some deep aerobic fitness. Training in the "junk" zones is kind of a wast of energy. I made a lot more progress after i stuck to doing long slows for months than flailing away in the junk zone for the same amount of time.
Training in zone 2 low 3 induces physiological changes in your body... This kind of fitness doesn't show up as clearly on short paddles but when heading into hour two of a race or long tempo paddle with others it makes all the difference.
www.slideshare.net/mobile/clarindabrown/...-to-aerobic-training
Training in the "junk" zone gives you nether the Arabic benefits as quickly or is hard enough to gain strength from interval training. It also allows you to train and not hurt yourself. This is very important to old farts like me.
Doing the proper ground work now will pay dividends later. It most likely will help your back as well by not injuring it while gaining core strength. You also might find that making your goal of 12kph over an hour? Might be a bit further out than 3 months. After the initial big and satisfying
speed jumps when beginning, those 10ths of a kph come slower and slower and with a lot of hard work.
Bill