Why use an organic at all in your mix? With my ficus, I go with the holy trinity, scoria (crushed lava rock ), some sort of pumice, and akadama. Sift the dust out and put it thru screens so you get a uniform size (don't mix big and small soil componenets together, or they sit to close to each other eliminating air spaces. Average size tree, use between 1/16th and 1/4'' particles . Use 1/4th to 1/2'' as a drainage layer. For shohin trees use 1/8th and 1/4'' soil particles in your mix).
Then, use a top coating of either shredded new zealand sphangnum moss or here is a top coating recipe I got from Ryan Niel. Use half dried out green moss like the kind that grows on the surface of our bonsai pots, and half new zealand sphangnum moss (must be new Zealand sphangnum moss, it's usualy sold as orchid moss. I get it at Loews). push it all thru a 1/4'' screen and then sift out the fines thru a 1/16'' screen. sprinkle liberaly on the top of your soil.
This will bump up the humidy, eliminating the use of organics in the actual soil mix, plus it will allow your trees roots to colonize the soil all the way to the surface where the best nutrition is and the most O2. It's like planting the tree in a larger pot.
I use this top coating on all my trees, and the soil temp's remain more stable and root friendly.
Ficus are tuff guys, and you should do well.
Thanks