I planted a Dharuma last fall, so it is finishing its first season in my garden. It has the lacier flowers that I like, similar to Quickfire, rather than the dense panicles of something like Limelight. Mine is in full, all day sun like pretty much all of my H. paniculatas, though currently it is somewhat shaded by tall phlox since the shrub hasn't grown tall yet, so I am not sure that my experience is of help to you.

I'd go ahead and ask on the hydrangea forum, specifiying which variety, but also commenting that you want info from folks at a similar latitude (there's one regular poster there from PA which would be similar) and similar light levels. IME all H. paniculatas have similar preferences so you can ask about the light levels in your heading. I think that 4-5 hours would be enough for good flowers since 6 hours is considered full sun, but the quality of the shade is important also. Is it bright shade from reflected light or dappled shade with some sun coming through leaves? Or is it dense shade caused by an overhanging dense tree? Is the sun only early and late in the day (less intense) or do you have some mid-day or afternoon sun?

Or you could just plant it and see how it does . . . do you have another spot you could move it to with more sun if it doesn't bloom enough for you?