I bought a #19 a few days ago and also had issues with voltage drop - .7v on a .8 ohm coil with Panasonic CGR18650CH's.
I removed the magnets and gain a few 10th's. I also tried the copper wire mod from this thread, but didn't like how it affected the throw and it made the switch feel like it was grinding. I remember I bought this and never used it a few months ago:
Hakko Cleaning Wire, For 599B Tip Cleaner - Amazon.com
They sell something similar at Radioshack for $10. I cut a piece off and shoved it into the switch -
Voltage drop is now .3v which is right in line with my other mods and the battery spec. The switch throw is the same and it feels smooth.