The amount of time you will spend on fixing it is almost as much time as doing the full 1/4 in my opinion and it will never look as good down the road. Sanding that damn curve is a pain and is a lot harder than the top of the sail panel. You also get to get rid of the seam you can see from the inside which will always reduce the value of the repair. If you can fix the the quarter the way it is you can fix a full 1/4. If you have to pay someone to weld the new one up it won't be much and will be worth it as it will only take them a few hours ater you have it already in place to do it.
You can do it, have faith in yourself if you are not sure, it's easier than it looks. Unless there is absolutely nothing else wrong with the panel go for it.
