-- Last Updated: Mar-16-13 11:42 PM EST --
How much IS that registration fee anyway? We don't register paddle craft here in Wisconsin, but I have two small motorboats and for each of them I pay $22 for a three-year registration. I could save that same amount of money by eliminating just ONE "major" daytrip every three years (it's not hard to spend 20 bucks on fuel these days). You live in Iowa and decent water for paddling is likely to be a whole lot farther away from you than it is from me, especially once you decide you want some variety, and your registration cost is only $12 for three years, so even if you have a car that's cheap to drive, I'm betting that what you spend on fuel to go paddling will eclipse the registration fee in a very short time.
You can see where this is going. Why cram a 230-pound man, possibly even with a load of camping gear, into a boat that's likely to be a great fit for a 120-pound person for no better reason than eliminating a cost that's insignificant compared to everything else you spend money on to go paddling? My guess is you haven't experienced what that extra weight does to the performance of a small boat because you've never paddled one while weighing 50 or 60 pounds less than you do. I haven't read about the boats you are considering, but if they are like a lot of boats, it's likely that the "reasonable" maximum load is about two-thirds of the load that's actually listed as the maximum, and even that load will be more than what's ideal. Of course, one would have to check the specs and then work from experience with similar boats to verify this.
If you place any value on speed, you'd do well to get something a couple feet longer too. A 230-pound guy normally has enough power to comfortably propel a longer boat. Many people in 12- to 13-foot boats spend too much of their time paddling at a speed that's too close to the boat's maximum speed and waste lots of effort as a result. I see it a lot with strong guys who are beginning paddlers - they don't know that they are exerting twice as much paddling effort as they'd need if going just half a mile per hour slower because they don't know they are in that range of speed where every fractional increase in speed requires exponentially more effort to attain. Do you see a pretty noticeable wake at the tail of your rec boat at the speeds you go? If so, you'll really be happier with something longer.
Of course, some people need a shorter boat for maneuverability on small creeks or for some other reason, and that can override the problems of putting too much person in too little boat (whitewater boaters do this to the extreme, but their boats are dog-slow on the flats too - that's the tradeoff). Only you know how much of what I said above might pertain to you.