One of the things I think is really helpful and I'd like to do more of is paddling an unlimited board occasionally. I don't own my own and truthfully don't plan to unless someone wants to offer me one to ride. I can't justify the expense right now and the storage is a bit more of an issue for me than it is for a 14' board. That said, any time I've had the pleasure to paddle a nice, fast unlimited board on fairly calm water I've really enjoyed it. I'm curious about racing on one though don't really have an interest in racing against the smaller field that we usually see in unlimited races. I love being in the race with the bulk of the competitors, however maybe one day I can go head to head with Thomas Maximus in Newport Harbour or something. We frequently end up finishing races together when he's on a 14' board. That would be really fun.
I've commented before that paddling SUP is a lot like paddling C1. The stroke mechanics are quite similar because the body position isn't a whole lot different. The C1 and SUP strokes are a lot more alike than any other paddling strokes that I can think of. The big difference between C1 and my 14' SUP is the weight of the stroke. The SUP stroke is far heavier than C1 no matter how much I try to make it light. The reality is that boards just aren't designed to be as fast through the water as racing canoes. When you put your blade in at the catch in a C1 the boat accelerates easily and rapidly in comparison because there is so much less resistance to it moving through the water.
To me, an unlimited board feels much more like a C1. Being narrower and longer it moves through the water much more easily than a 14' board. It accelerates more easily and glides much better between strokes. As a result the stroke to me feels much lighter.
The reality is if you want to accelerate a board or a boat you have to have your paddle working against the water dynamically. It needs to be working against the water faster than the craft you're paddling is moving through the water. If you begin your pull and the board or boat speeds up to match your pull it won't continue to accelerate unless you do something to provide more impulse. The easiest thing to do is increase the rate at which you apply force against the water with your paddle. This will result in the board or boat continuing to accelerate.
You can try this for yourself. If you paddle and move your blade slowly against the water your board moves slowly and doesn't accelerate much beyond the initial acceleration at the catch. If you think of accelerating your blade through the water (actually you're accelerating the board by the paddle) your board goes faster and accelerates through the stroke.
In every paddle sport, whether it's canoe-kayak, outrigger, surfski, dragon boat or SUP, this principle applies. So if you want to be fast you need to sometimes do things to train yourself to pull more quickly against the water than you normally do. Paddling on a board that moves faster than you're used to is exactly that. If you do all of your paddling on a 14' or especially on a 12'6" board, you'll notice when you get on an unlimited that your stroke feels too slow for the board. You don't have good connection because the board moves so much more quickly that it gets ahead of your paddle. You've got to work more dynamically with your paddle to keep up with your board. Doing this regularly trains your nervous system to perform your paddling technique more dynamically while maintaining the efficiency that you've developed on your slower board.
How is this useful for paddling on the slower 14' or 12'6" board you spend most of your time on? Well, if you can increase the speed with which you are comfortable working against the water on your slower board without losing any efficiency you're going to make it go faster. Track athletes do something similar in their training to increase their sprinting speed. They call it over speed training and will do things like run on a treadmill at faster than normal pace for short periods or get towed at faster than normal pace. In kayak, it's not unusual to see K1 athletes spend time training in faster crew boats like K2 and especially K4. A K1 athlete in K4 has to learn to move much more quickly to find the same connection he feels in his K1. After becoming comfortable with this faster, more dynamic movement he can apply this in his K1 and perhaps gain some small increment of speed through his more dynamic connection. In races which are decided by very narrow margins this can make the difference between making the podium or missing it.
I tend to have a slower, more heavily loaded stroke than many. I'd benefit from gaining comfort with a slightly more dynamic, lighter gear. I might not use that gear all the time but having it would certainly help make me a better sprinter. Paddling on a faster unlimited board once a week would not only provide some variety but would help me develop my stroke in that regard. In all likelihood it would for you as well, so if you have access to an unlimited board on a regular basis take advantage of it.