Just a quick thought,
Yes there has been a Woma(aspidites) X Ball done before, it is called the "Wall" and was produced by Kevin at N.E.R.D.
Also, a Woma(aspidites) has been crossed with Morelia as well (Irian Jaya Carpet Python) and was also done by Kevin.
I'm not saying that you couldn't cross a Carpet with a Ball, but I believe what is truly happening here is that the Woma is much like a preserved version of an ancient early python line(minus the heat pits) and therefore if both carpets and balls speciated out from an ancestral stock such as a woma, then this would mean they are backwards compatible with Womas(as they are) but this does not necessarily mean that they are cross compatible with each other, and I would expect a much lower success rate.
Hope this make sense, typed it real fast at work, if anyone has any questions feel free to ask.
-Dan