Yes, a down angle will work fine.

Here are my thoughts on the subject. First off, if someone really wants you camera, they will get it no matter what. I have heard of python locks cut with bolt cutters, and even trees cut down with a chain saw. Locks and such keep honest people from being tempted, and may be too much work for lazy thieves, but if they really want it, it is gone. Best bet is for them to never know it is there.

All of the land I hunt is private, and most of it is pretty secure from trespassers, but not all. First off, IR is best for hiding, and you have that covered with the no flash. A big white flash screams "come steal me". Second, don't put the cam at eye level where it is easily seen, up high out of line of sight is good. Removable steps and such to make it hard to get to are even better. Put a python around it too, and then you are talking real work to get to it and steal it. If there are some small limbs an branches that can help break it's outline then so much the better. Don't make a regular trail going to it either, if they follow your tracks in and they suddenly stop, they are going to be looking for what you were doing there and may find your camera.

I build my own homebrews, with hours of work in them. To lose one is more painful to me than if it just cost money. I protect them well when need be.