Hey Chris!

Yes the stretch is a killer! I almost feel like those guys wrote the lick out of some sort of exercise they were practicing -- it's symmetrical and a great exercise in itself to work on finger stretches, legato, and speed.

If you continue to drill the pattern for several minutes (or until your hand fatigues!!) each and every day, it should get easier and easier. Be sure to practice it slowly. Plenty of repetition at slower speeds will burn these tough stretches into your muscles, and with consistent drilling, you should see an improvement over time.

For myself, I find anchoring the index finger onto the fret helps me, but I wouldn't discourage you from experimenting and finding the right fingering technique that works for you. As guitartists, it sometimes takes that experimentation to find a technique or approach that seems more natural to us.

Hope this helps! Let me know how it goes,

Mike