Dwight :

Here are a few thoughts . The link below is on stct./habitat.
http://www.sdafs.org/reservoir/manuals/habitat/Main.htm

I like your plan so far. Different types and sizes of fish use different cover size ,location, depth ,etc. Any plan should be designed to fit the needs of the owner/goals and the pond and viewed as a whole.

WRT the pvc ones above I would not put them all in one group. I would keep my options open. The good thing about them is they can be easily moved/changed. I would try several groupings in different locations ( 3-4 in a line , several in a triangle or other shape, some down a point in different depths , some out from your tree line stct. or post stct.). If one works better than others then change them up. See what works -- run a fish finder over them after they settle and see what it shows.