chuck
a couple of things to keep in mind when selecting staves from a leaning tree.
the compression side of the tree, (the side facing the ground) is often different from the tension side,(the side facing the sky)
Generally, conifers make compressionwood on the ground side to enable the tree to deal with the lean induced stress. While hardwoods make tensionwood on the sky side to help with the same.
as you might imagine, having compressionwood on the belly might be a plus, but that is not easily accomplished as the back of the bow has to come from somewhwere in the middle of the stave.
having tension wood as the belly could be dissapointing, hence I would be inclined to avoid the tree you describe as having deflex on the back.
that being said I, must qualify my response by saying junipers are not like most conifirs in many ways, and my experience with them is none, so comments from anyone with specific juniper experience would be welcome.
I do know from experience that trees with compression wood or tension wood (known collectively as reaction wood), do not make good bows if the bows back comes from the side of the tree such that one edge of the back has reactionwood of one kind, and the other edge, the other kind. Hope that is not too confusing.
On thing you might want to try to do before cuttting a live leaning curved tree, is to examine a crossection of a similar juniper (perhaps by cutting a dead one?)
the foregoing is also something you would want to consider about branch wood also. Since the NA bow makers are reported to have utilized branch wood for staves, understanding where the best compression quality wood come from might be worth some investigation. Although I know that you are not building a sinew backed bow as the NA often did, having a good belly is always to be desired, as it is where most flatbows reach their limit by taking set or othewise failing.