Hi Jacob, another material to use is ordinary particleboard (if that is the correct English word). I find it somewhat less fragile than mdf. Just my taste I guess. But my input in this discussion is another than the material. Instead of making a solera you could consider making a slightly more versatile system that incorporates a very thin plywood solera on a base.
Here is the base. My is made from scrap that happened to be both plywood and particle board (the plywood on top) but since the material was dry and my workshop is climate controlled it has worked without warping. Anyway, the base is a sturdy wooden beam on which the workboard is attached. The workboard has slots cut out along the body line. You will soon see why. The neck part has no plywood, only the lower layer that consists of the particle board.
http://i194.photobucket.com/albums/z150 ... en/h17.jpg
On the neck part I can fit plywood wedges and thus choose what neck angle I want. My finger point at the nut position and it is lowered 2 mm (in this case). If I want a steeper angle I just change the wedge to another. Since I use the same type of baltic birch plywood it fits right in at the body.
http://i194.photobucket.com/albums/z150 ... en/h18.jpg
Here is the solera positioned at the workboard. It is made from 10 mm plywood but any material can work as long as you can scoop out the doming and it is flexible enough to be bent over the body/neck angle. My finger points at the scooped out part of the solera. In this case it is domed by ca 2 mm.
http://i194.photobucket.com/albums/z150 ... en/h19.jpg
Here is the neck and top positioned on top of the solera. A bolt through the beam/workboard and soundhole is holding a small wooden block pressing the top against the solera. Two clamps is holding the neck. The neck angle is defined.
http://i194.photobucket.com/albums/z150 ... en/h20.jpg
Here are the sides held against the top with spool clamps. A couple of side supports is helping the sides to find their correct outline. At the end block is a heavy block attached to the work board as a support for the smaller block of plywood that is fitted between the big block and the sides. This smaller block has the curve of the body outline against the sides and is flat against the big block.
http://i194.photobucket.com/albums/z150 ... en/h21.jpg
To conclude. With this system you can build any guitar shaped instrument, with any neck angle and any doming by changing neck wedge and solera. I am sure many luthiers around the world are using similar systems since it is a natural development of the traditional solera.
And by the way, those pictures are not taken for this post, they are a part of a more than 200 picture long photo essay I have done on two Swedish guitar forums and one English flamencoguitar forum.