I put a 2x4 across the top of the skylight, had an assistant hold it
level, and measured the height on my '84.  6' 9" exactly.  My springs
have probably sagged a bit!

I never enter a garage with less than 7' of posted clearance, which
usually means you have 7' 1", since they tend to give you a little more
than advertised. Never had a problem.  Any less and you are risking
bouncing up and scraping something with your expensive skylight, like
one of those low hanging sprinkler heads.  What fun that would be!

--
Stuart MacMillan
Seattle

'84 Vanagon Westfalia w/2.1
'65 MGB (Daily driver since 1969)
'74 MGB GT (Restoring sloooowly)

Assisting on Restoration (and spending OPM):
'72 MGB GT (Daughter's)
'64 MGB (Son's)

Stripped and gone but their parts live on:
'68 MGB, '73 MGB, '67 MGB GT