I like the idea to place them vertically, but I think they need holes drilled in them for water circulation so they don't hold somewhat stagnant water.

I still might cut a big scoop out of one side about 1/3 the length of the culvert. I think LMB are far more likely to practice their ambush predation by launching out sideways, rather than straight up.

I also like Al's suggestion for pipe insertions that are more "bendy" than PVC. A good cast would go just past the edge of the material. However, if you miss too close, then you could still drag a lure through your structure without getting snagged.

I would also utilize the plastic scoops that were cut out of the culverts. I would drill holes to stick 1-2 pieces of larger PVC through them so they would stick up like the WWII obstacles put offshore of the beaches to prevent boat landings. Add as many pieces of bendy pipe as you want. You might need to drive one piece of your PVC pipe into the bottom to hold it in place, or cap one piece and fill with sand or concrete.

Good luck on creating some good structure for your fishes!