I would like this information also.
There is some stuff out there about getting it going with 6.x and some folks who claim to have done it (search/find, etc., etc.).
I got errors on my first attempt with 6.0 so I fell back to 5.5 to make it work; LAN to LAN to LAN.
Anyone who could write a "high-quality HOWTO" for IPSEC on SME 6.x will be a hero and deserves big bragging rights!