consumers spend very little time on the thank you page, they're done. i don't worry about it where i use it and have never had any consumer complaints or questions about it.
Also, if it is at the bottom I worry that some people may not load it. My conversions went up when I just changed the placement to the top. It was a very small number, but a noticable change nonetheless.
I would not worry about the tracking code too much. What bugs users the most is SLOW loading pages, and confusing pages.