Have another look and think about the track systems. With the right creativity they can be easily incorporated into a new build and made to work almost seamlessly with finished floors. There are also "pockets" with individual attachment points which are great alternatives to the longer multi-position tracks.
Give these guys a look: http://https://www.cargoequipmentcor...ducts-s/38.htm
The D-ring attachment points are great if that's all you need and want. Placement would really depend on your use, there's no one best or right way where they're installed.
If you're anything like me those after-the-build-is-done regrets can drive a person crazy, coulda woulda, shoulda done this or that or yada yada yada.