Finally building up my EAI Bareknuckle frame. First thing I tried to put on, after the fork was attached, was the seatpost. But it wouldn't slide in. It slips in about a centimeter and a half, after which point it would require a good deal of force to make it go any further. The post is 27.2, which from what i've read seems to be the correct size. Thinking the post might be defective I tried a different seatpost today but it still would not slide in. I've never come across this problem and certainly didn't expect it from a $700 frame. What should I do?