we tie a medal rod width wise across our slip. Put one at bootum of christmas tree and one at top. Weight down with blocks and lower in. It keeps the trees upright so you can fish around them.

That was the key thing this guy did in his slip. All 4 trees where sunk so all were upright. It helped keep you from getting the jigs caught in the branches. It at least gave you a better chance of getting them out when you did get one hung.

I like your metal rod idea. Attach the trees to the rod and the weight to it also. I like the idea of the metal rod on top so you make sure they are upright.