Parallels window problem
I had the exact same problem. I went a different route, and decided to sacrifice the nice high-DPI of the Retina for a scaled solution that makes everything look right.


In Parallels VM Config → Hardware → Video → Resolution

Use: Scaled
Not: Best for Retina, More Space
Restart VM
Windows Display Settings → Set Resolution: 1280x800 + Apply
Windows Display Settings → "Make text and other items larger or smaller"

Use: Smaller (100%)


Late-2013 rMBP 13.3″ with Parallels 9.0.23350 and Windows 7