HI David
PM Sent, but basically from what I can remember I had a couple of hard Balsa strips,( Might have been a firework stick) , I soaked one end and then let it dry with a curve in it. Then glued the main flat section, let it dry for a day or 2 and then with some good wood glue and some hefty clamps glued it to the curve and left it for a few more days.. Has not sprung yet !!
Larry