Here's how I mounted the longbow limbs to my metal riser.
The riser and the compounds limb rocker
(http://i122.photobucket.com/albums/o241/galnmax/Strongbowlimbmount1s.jpg)
The longbow limb with holes drilled to match the rocker
(http://i122.photobucket.com/albums/o241/galnmax/Strongbowlimbmount2s.jpg)
Rocker mounted on the limb
(http://i122.photobucket.com/albums/o241/galnmax/Strongbowlimbmount3s.jpg)
Limb mounted showing the spacers added to the sides of the limb
(http://i122.photobucket.com/albums/o241/galnmax/Strongbowlimbmount5s.jpg)
(http://i122.photobucket.com/albums/o241/galnmax/Strongbowlimbmount6s.jpg)
Works great and doesn't look too bad either.