\definemakeup[titlepage][pagestate=start,doublesided=no]
\setuplayout[titlepage]
[backspace=2cm,width=108mm] % 148mm is the width, 20 mm of backspace,
\bfc This should be the long, long, very long title\par
\stoptitlepagemakeup
This is the colofon
\chapter{Start here on page 3}
\dorecurse{20}{\input tufte\par}