C-Forum

I am looking at buying my first slalom C1. I weigh 110# and the boat is rated for 140-170#. How will being underweight affect boat performance? I cannot try the boat out since it is on the opposite coast.
We Canoe

It depends on your previous experience with low-volume boats. If you are a newbee, you are not going to be doing mega-pivots for a while, and I wouldn't recommend you do so. But, while it will be more difficult, the new boat will allow you to learn the technique. Of course it also depends on the boat: older boats are much less radical than the newer designs, so any pivot might be really difficult at your weight.

On the other hand, if you did find a boat appropriate for your weight right now, depending on your strength and experience, you might find yourself over your head for quite a while.

Lots of other factors come into play: age, sex, previous paddling experience, etc. It would help if we knew more.

Newbee with 3 months experience. I currently paddle a Zealot because it has been very hard to find a modern slalom boat. I am looking at a What Else. I am strong and paddled OC1 class III for three years and ready for more challenge. I plan to focus on slalom next year as a junior paddler. I really need a modern boat, so I am very tempted to get it. I do not expect to get any heavier.
We Canoe

The What Else is a very aggressive design, so be aware that there will be a big learning curve and a lot of commitment required. I would get in touch with Galasport and get some recommendations on model and cut for your experience. I hope you have a local spot where you can paddle at least several times a week, in gates or a reasonable facsimile, and in whitewater as much as possible.

Good Luck!