I have loads of dwarf bamboo we use for arrows here in Taiwan. Damn near invincible. The spine the aboriginals use here is very low. I do not have any lower spined shafts right now and hate trying to spine boo. It is a serious hassle, but I could ask some local guys if they've got any extra low spined shafts. We normally pick them in the late fall near the top of the front range of mountains. About 1km up. The higher stuff is better to a point. I have fields of them at my disposal, but it is always hard to know the spine before it dries. To be honest, I'd just as soon pay someone to do it for me. There was a guy on one of the FB primitive archery groups selling spined shafts. Seemed pretty reasonable.