Hi Simon
I like this site:
http://www.reinervogel.net/index_e.html
However, I would recommend you have a close look at one or preferably both of these books:
http://www.willbell.com/tm/dobtel.htm
http://www.willbell.com/tm/PortableN...Telescopes.htm
The second book by Albert Highe is the one I like more and would I think lead to a lighter scope. The Krieg and Berry book is excellent too. It shows you how to build an obsession style dob. Some of the ideas are looking a little dated now - eg the main mirror cell and the truss clamps. Highe's book and the web site above have simpler solutions.
Make sure you read the sections on balancing your dob. It's easy to wind up needing to add a ton of weight to the mirror box if you don't.
Also consider whether a lighter solid tube and mount might suit you better. Commercial scope dob mounts are often made of heavy chipboard and have excessively large circular bases. You can save a fair bit of weight by rebuilding the rocker with plywood. Octagonal or round tubes made of ply can be very strong, light and attractive. I'm seriously thinking of converting my 12 inch truss dob to a light solid tube to save on set up and pack up time.
Hope that helps.
Rod.