Dowl rods mold quickly. The rod holders are great! I use them in almost all of my cages. The others are neo cages and just have PVC ran all the way threw. If you want easy removal build something that has support and sits in the cage. Kind of hard to explain but pretty much make an "H" and add another cross bar below the top so the bottom is on the substrate and the top perch isn't so tall the animal won't be cramped. Habitat systems (I think) uses this design. I've seen them and taken them out and they are probably the easiest to remove, but are best suited in tubs or top open cages. If you're going with glass use 100% silicone and measure and mark the outside of the glass with dry erase marker. Let it air dry outside for atleast 24 hours. I have a pic I will post of this method and natural wood. I really liked it, but got away from glass cages.

This method works really well, but use plastic screws.