You might consider building a bypass of 1" pipe/hose around the heater but still keeping the heater in a straight line with the pipe. This way the water will want to continue in a straight path through the heater but the water that is choked by the 5/8" orifice will be routed through 2 X 1" T's and 2 x 1" 90 degree elbows around the heater.
I scratched my head about that one for a while. I hadn't thought of your idea, and will certainly give it a go if I'm not getting the circulation I want. For what it's worth, here are updated pictures of the plumbing and stand interior.
One picture below shows the whole works, the other shows the plumbing without the filter so you can see what I did to plumb in the water supply.
I modified a PVC reactor so that I could use it as an "input" for water into the tank from the faucet shown in the picture. The faucet allows easy top-offs and water changes, but I'll still use the old hose-to-toilet/lawn approach to drain. (There wasn't any good way to plumb in a waste line, or I'd have done that in a second...) There's a ball valve on the reactor that I can use to isolate the water input. The gray tee on the inlet side is just a bit of future-proofing. It lets me attach anything I want to that 3/4" threaded port. The most obvious use I can think of now is a dedicated drain hose, but for right now I think I'll just go over the tank rim for my water changes.
I've also included a shot of the bizarro reflections that the array generates--at least when there's nothing in the tank to absorb or diffuse any light.