Here is something else to consider: If you want to 'test the waters' you can start with the center section of the wing you choose. Figure out the proper selection of wood and buy only that amount of wood. Cut the ribs, set up a building board, etc. If you find you lost interest in cutting your own parts you can quit right there and you will not be out too much in terms of time and effort. If you find the experience interesting and want to continue, work on the outer panels. If you finish both panels you can try building the tails parts. Having gone that far you will be faced with only the fuselage, which is rather straight forward.

One other thing to keep in mind when building by hand is that you become very inventive. For example I was forced one time to make a 1/8'' thick length of wood from surplus 1/16'' balsa sheet material. Using Aliphatic Resin I laminated two pieces of 1/16'' sheet stock (just a little wider than I wanted) and then used a straight edge to cut the width to the proper dimension. What I ended up with was a rather STIFF yet LIGHT 1/8'' strip of wood. This was interesting. I generally use this technique to make ALL of my tail surfaces now. I have even considered making an entire sailplane using only 1/16'' sheet stock and laminating it, where required, to make thicker stock and using spruce, etc. where appropriate.

It appears from another post I saw you had made that you have experience building fairly large sailplanes. So the decision to scratch build shoud be a little simpler that I first thought. You already know what is required to finish a kit sailplane so you only have to ask yourself if you have the patience and the drive to cut the parts.

I know for a fact that if I could not build planes from plans or from scratch I would have lost interest in the hobby a long time ago. That is how much I enjoy making parts and building a finished sailplane from those parts. If I had balsa trees growing in the yard I would be one of those people that would prefer to cut my own trees to make my own wood to make my own parts to make my own planes ... and I actually have made a fuselage nose section for an Aquila sailplane from a tree I cut for firewood. It flew very well ...