I use pine structural beams, I don't know what they are called in the USA but here they are sold as L.V.L. here. It is just pine laminated vertically to make the beam, a lot like action wood but used for construction in houses. It's light and strong and very stable, mine don't warp or move and I have fired mine in the heat box many times. I have seen the product in the States, she is ready to make into a bow form...Glenn...