btw, shipped radvd is quite old - 0.7.3, here's the changelog up to the last 1.5
http://cvs.litech.org/viewcvs/radvd/CHANGES?view=markup
size comparsion:
radvd-0.7.3 58Kb, ~20Kb inside FW
radvd-1.5 91Kb, ~28Kb inside FW
Is it worth to?