Too many stones missing to restore it, or should that be too littlestone(s). There's many books and website that have a go at showing it how it was, complete, and of course Foamhenge did a pretty impressive job. Without the missing articles it's impossible, but assuming that the lintels were all at the same height, and that the surviving stoneholes don't lie, then the current models are probably not too far off the mark.......until the majority of the site is excavated for the first time.
Cheers,
TE.