My finding of juniper in my home central Oregon is that the heart wood is decent compression and the sap wood excellent tension have made a few all sap shot smooth and fast crysaled horribly. Tried all heart wood twice both exploded during tillering have made good ones with out sinew just rawhide. +1 on limbs and sky side is best, usually (the sap wood is thinner on the up side: Keenan pointed this out to me) and has more tension taking less set. when you look at the tree pay attention to the bark if tree has a brownish bark it will have dryer brittler wood and almost always hollow center. Look for bark that is grey in color darker better, best luck will be on hillsides and in draws. Worst luck will be on the sandy flat of the dessert and the trees on the tops of knolls will be far more likely to be twisted badly. The book Ishi suggests that it has to be high elev. Juniper but I've cut trees well under 3,000' and near 6,000' elev. and I can't tell the difference.
P.S. research Pacific Yew the needles and Cambrian layer has medicinal values helps the immune system and is been researched for it's taxinol for fighting cancer.The berries however are poissones. Quite a remarkable tree if you ask me it can give and take life in multiple ways. The juniper as well has medicinal quality the berries on this are edible but as Crocodile Dundee would say " You can live off it but tastes like S@#!.