One method I found that works to build your tolerance a little is to read a book upside down. Go home, lay on the bed on your back and hang your head and part of your body off the edge upside down. While doing this concentrate on what your eyes are telling you, not what you are feeling. You can also watch TV, the picture will be upside down of course but your mind will eventually see the picture right side up as you become used to it. You feel that your body is upside down (your guts move up in your stomach) but the TV or book will appear normal. If this makes you a little nauseous thats good, just push on through it as this will build the tolerance.