Differences between Magnepan 1.6qr and 1.7i

I owned MG1s way back in the '70' and a year ago picked up a well-worn pair of 1c's for $100 and fell in love with the "Maggie Sound" all over again.  But I've been using Thiels for years, and no longer can live without high transparency.  Also my room is a little small for the 1's and probably would be better with a slightly smaller speaker ... thus my interest in a pair of used 1.7i's or 1.6qr's.  My understanding (but not certainty) is that these are basically similar in materials, technology, and concept.  Can anyone confirm that who knows both.  And if then the big question (if similar):  how different do they sound.  My internet browsing leads me to believe that the main difference is in the high frequency balance, with the 6's perceived as a bit (too much) brighter?  Again, anybody heard the pair side by side, or at least in the same environment.  Any such info would be appreciated.