Nice work Lance-engineer boy <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt='

'> That's good stuff!
To the last couple, IIRC, the formula assumes unlimited horsepower (i.e., wind resistance will be overcome). This would allow you to reach the mechanical limits of gearing. Also note that wind resistance ("drag") occurs at virtually every speed, becomes noticeable above about 50 in most cars, and usually limits top speed in cars w/o governors (w/o unlimited hp).