Hi Jonathan
I don't know too much about the pneumatic carving tools--I am new to carving completely. However, I can speak from experience about pneumatic tools in general. I have included a link to a page that I saw had an adapter that will allow you to use large mallet type carving tools with an air hammer normally used in automotive or rescue work.
http://216.106.57.170/~bigdog/35.htm
I have used air chisels and impact wrenches for the last 25 or so years when I performed and taught vehicle rescue. From my personal experience, Chicago Pneumatic or Ingersol-Rand tools usually held up the best, were reputable, and were easy to get repaired/maintained when needed. Of course, as always, it goes without saying that the name-brand usually has a bigger price tag. One of the most important things to bear in mind when using the impact tools is to make sure the compressed air is dry and lubicated. If you're using a compressor without an air dryer/lubricator, then you can expect to have to repair/maintain the air tool a lot more--especially in an environment where air temperature changes a lot and causes condensation to build up in the compressor's air storage tank. The moisture causes the inside of the impact tools to rust and gunk up with dirt. The dryer allows the moisture and dirt to be filtered out, and the oiler keeps the tool free of rust and ensures the mechanical parts of the tool move freely. Hope this helps.
Bob