STTB is definitely the best first start.... don't know what's up with it right now. Hopefully it'll be back online soon. www.spadworld.net
is the main discussion forum for SPADs. Chunky C has a great web site
with a ton of plans on there including most if not all of the original plans plus a lot of good tips. ChrisSPAD has a lot of good pics on his web site
and a great tutorial on designing your own SPAD. There's also a good web site
in the UK slanted mostly towards combat but a lot of good plans and tips there as well. Good luck with it!