Prop bin setup

I have a Ludisia discolor that has gotten badly stretched and leaf bare over the past 5 or so years. I would like to chop it up and attempt to propagate it. I also plan on propagating some other plants in the bin, such as ficus pumila, ficus quercifolia, and a couple other plants, that I have in an established terrarium, that I don’t know the name of.

After reading and doing some research, I assessed the materials that I have and came up with the following substrate formula.

3 parts chopped sphagnum

2 parts chunky perlite

2 parts coconut husk chunks

2 parts reptibark

1 part small size pon

1 part horticultural charcoal

I used dechlorinated tap water to rehydrate the moss. When I squeeze the substrate, it does not drip water. It feels lightly damp to the touch.

I also added springtails.

Does this sound good? If need be, I can take it all back out and remix/adjust the ratios.

I have a leca false bottom that is about an inch deep, capped with plastic canvas. On top of that is about an inch and a half of the substrate. The whole container is about 6 inches deep.

My next question is, is the substrate deep enough? I need to balance substrate depth, with headspace for plants to grow.

Any other suggestions or advice would be greatly appreciated.