I'm not sure how much you can read into these (link below) - L Stroll being at the top leads to a few questions (braking far too late?) - however I still find it interesting.
From this it appears McLaren are not in such a bad position (which is backed up by Alonso qualifying in 13th, however I think that was more attrition of other cars/drivers). McLaren are only about 10km/h down at vmax and on par with Ferraris 2016 PU, which isn't all that bad considering they are still technically a year behind in the development timeline. Law of diminishing returns should have them close by the end of the season, providing they can get their reliability sorted.
http://www.fia.com/file/54531/download?token=PPrtPc2p