Steve,
This question was asked about a week ago and "Trashwood" gave the following answer:
"Bob Gordon, from "You can't find him", Iadho, takes old bear, jennings and proline risers and converts them very carftly to accept the limbs with ILF (olympic) fittings. He will wait the pottom limb pocket, and build the shelf to shoot off of or you can use a flipperl/plunger. my limbs gain about six pounds from their longst posted draw weight for example 68" 40# longs give em a 65"ish bow and 46# draw. Bob's risers are geat risrs. ya get more bang for the buck that any other riser out there, I have shot my PB ibdoor 300 and IFAA field match with Wor riser and Borber TXg's.
rusty"
Does that help? I have seen several and shot a few, but not my cup of tea.