A dikdik is not even close.
Personally I would buy a head form that is close and I would carve the body. It is a pretty simple shape to carve even with out any thing but the skin for reference and most the time I will wrap legs (or part of the legs) for a small lying down mount. Another thing that will help is to carve the body just a little small........ and mix vermiculite in with your hide paste till it is about like a running peanut butter. use a thick layer of this hide paste on the carve form and you can sculpt and shape from the out side of the skin once you have it zipped up.
Here are a couple of photos of a bay duiker that I carved. It is a little rough but keep in mind I put much of the detail in with the vermiculite/ hide paste mix once it is mounted.



Also when there is not a form or a good choice of form I will use the actual skull or at least the top of the skull and sculpt the rest in critter clay.