Welcome to Camera Labs! Just read your post, and although I have absolutely no practical information regarding product photography, I think your question will be better served if you post it in the Going Pro?
or possibly even the Off-topic
sections of the forum. There are very few Pentax users here, and as a result this particular area sees very little action.
Since your question deals with photography in general, as opposed to specific questions about the K7/Pentax, you won't be breaking any rules posting elsewhere, and you'll be far more likely to garner a response or two in the higher-traffic areas of the forum.
Nikon D300 / 35mm f1.8 / 300mm f4 / TC-14E II
Pentax K200D / DA 18-55mm / DA 55-300mm