6' - 255 lb. and no problems at all. The 987 is roomier than the 986s I test drove, but I drove my avatar at 235, so, tight fit in a Boxster? I doubt it!!
The cayman does seem to have more headroom than the box, but, maybe because you know the top won't go down, the cayman felt a little "clostrophobic" to me and the box doesn't......?