1: Keeping the drainage hole OPEN and free of roots is very important. Ive never got used to metal mesh. I use plastic(needlepoint ) mesh and COPPER wire staples. The galvanic [electrical charge] action of copper or galvanized metal [I ASSUME] irritated the roots and bugs. Keeps drainage OPEN. This is good. Copper and the zinc coating is slightly poisonus.
2: At a Ryan workshop we repotted a about a dozen ponderosas. All were tied with 17 ga galvanized horse hotwire and screws or chopstiks. Everyone one of them I have seen since then are crazy healthy. My 2 are absolutely amazing.
3: I use about 14ga steel wire. Works fine. Wont rust fast enought to matter.
4: the wire is fine. I think the quality of the type of wire is the reason. It doesent oxidixe at all.. t’s tensile strength is the reason he uses it. Aluminum and copper stretches. Tree gets loose and moves. Kills roots.
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I always tie down with steel wire; always use copper wire on the drainage mesh.
I’ve done bonsai since about 1970. I’ve learned more into the last five than the rest. My trees are better because of Mirai.
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Balance of water and oxygen… hmmmm..ohm…