Our Strategy during our 10+ year "Project", was that we found the need for "Stealth" and "Hiding" all the cover we could! Grouping was based on how many we could put in an area and "hide it"! We would go out with the Best Electronics made, and "Look" at an area and figure out if it was possible and how we were going to do it...then after we took more "pictures" to see how successful we were!
We were trying to improve the overall quality of the lake and help the fishery, instead of making Honey-holes to attract fish to be caught easily!
In a large highly pressured lake, if cover is found, it is just fished to death...which pretty much makes that area worthless for increasing the population, so it expands and replenishes.
We put spawning and baitfish cover shallow and away from bank fishing areas, so it couldn't be found with electronics or shore fishermen. We also put cover in drop-offs, creek beds, in Big Rocky areas. PVC becomes Invisible and was used in great numbers...laydowns are hard to detect in the right areas...and wood was used in areas that most fishermen wouldn't take their boats, or where electronics would bounce or skim over top of it!
Let me say...that if you want to "hide" cover from others, in certain lakes it is possible, no matter how good your electronics are. If you have water color and content, plus good structure, and natural rock, or rip-rap, etc, etc...content based on location, is better than a constant grouping!
We did make 2 HUGE Freshwater reefs on deep mud flats between drop-offs...we used broken concrete rubble as a base, then concrete blocks, then 10 hole bricks on top! We marked off the areas with bouys, and dropped everything between them...it worked perfectly and stacked up nice!