Keywording Question - to add "ing" or not

Use sitting in the title, sit in the keyword list.

That is a question you can answer yourself. Search Adobe for "sleep bear". That brings 307k results. whereas, "sleeping bear" brings 306k results. Not much of an difference but, still a difference. 

Thanks all for responding. I found myself going around and around in circles today, trying to figure out which form is best and/or if both are necessary.

I suspect one would be sufficient, and I'd personally lean toward the "ing." And if you took your concern further, you could go crazy wondering if any of these are better: sit, sits, sitting, rest, rests, resting, perch, perches, perching.