Just finished building and tested a 10 element yagi for 1296. This antenna replaced the larger yagi that did not appear to work. This one received the source just fine. Being it is only 21 inches long (boom length), it did not perform like the 4 foot long antennas that I had tested earlier, it still seems to have the gain and directivity that I would expect out of a 10 element yagi.
The software that I used to design this antenna suggests that the antenna can be lengthened without having to change the current element lengths or spacings. Therefore, I'll add another segment to this antenna at a later time to increase its size to something that should be more useful.
This antenna was a new design, as I used very small diameter elements (1/16 inch). Most yagis on 1296 use 1/8 inch elements, which in my opinion might be a little large for this band. Although the software can design working antennas with different diameter elements, I went with 1/16 inch aluminum to keep the weight down, and I'm thinking the thinner elements might provide a little more gain.
The next step is to get these antennas tested for return loss. I still have no idea how they perform in that manner, and do not have the instruments to test. I did run across an article online telling how to build a directional coupler that works from 2 meters up thru 1296, which I just might decide to build. I think I have all the necessary parts to build it.