This topic has been discussed on this forum a lot. But the forums search function is not the best. Instead use google to search for: "site:forum.pjrc.com bottom pins".
You should find enough information to get a picture of what other's have done, including some breakout boards that provide access the bottom pins. You should find several alternatives in your search.
What Teensy are you using?
Is there any more you can reveal about your project or requirements?