If you can find a copy of Richard Berry's How to build a telescope (new from Bintel or possibly a copy you can borrow from your local astro club) there is a good description of an alt/az mount for a 6" f15 that could be adapted for a shorter scope.
Here is a link to a picture of one built by Jeff Morgan half way down the page
http://www.cloudynights.com/ubbthrea.../o/all/fpart/3