I'm sure your plane is non-certified, so I will suggest that you stop by biplaneforum.com and ask those guys. Lots of tailwheel knowledge over there.
Also, the RV forum may be of help.
I guess if your plane is light, maybe you could use a single leaf instead of a stack?
U30512-002 PIPER TAILWHEEL LEAF SPRING - MIDDLE - Univair Aircraft Corporation
For lightweight wheel assy, you could check out this one:
http://www.wingsforum.com/viewtopic.php?f=218&t=23464