Obligatory Sketch "we can do it too!": http://cl.ly/Vml2

any way sync scroll location on both PSDs?

This is how I used to work on @2x files before I had a Retina MBP. It's a great trick.

Old but gold.

Use this all the time when doing icons. I mean, I used to when I used photoshop for icons.

Been using this for years, really useful. Also great when using liveview and working at 400% on details at the same time.