Censu, here you have the supports, which Kosio made. He saw them in Dean Torges CD Hunting the bamboo backed bow.
They are used with a great wooden beam (as shown on the second pic of this thread), sliding longways, so the hight you'll reflex your bow varies. He made some couples with different height to be more convenient, but you could make some different wooden pieces to put in this thing like shown here.
These here are intended to give you a distance from the table, to can wrap the fixed bow for example. They don't have a slot for a beam and lie down on the table.