I purchased 3/8" by 3'' teak. Since my purchase, I have heard nothing but horror stories about installing such thin wood. I have been using a Bostitch M111FS to staple 1/2" Australian cypress with about 60 lbs. of pressure with good succuess. The machine does not have a 3/8" plate and I'm worried about the results I'll get. Does anyone have any hints that might save me a lot of troubel?

Your going to need a stapler with a less beefy staple. 18-20 gauge.

Senco SLF-20-HF
PortaNails 465
HighPro 4090-AS
Bostich Floor Runner
ProNails P-50

Perry is absolutetly correct. Your manufacturer installation guidelines shoudl spec what size fastner to use. And if they do not, that should be a sign to walk away from that product/manufacturer and go to one that does.