Since I clone in soil, I've never measured the roots. But regardless...I transplant when the new leaf growth is vigorous and healthy.

The technique bonsai gardeners use to re-soil their trimmed rootballs should work fine if transplanting from bubbler, into soil. Not too sure what happens with the rapid rooter if you do this, tho.

Set-up the pot you'll transplant to. (1" of drainage rocks on bottom, soil mix to within a couple of inches from top)

With one hand, hold stem upright and place the root ball on the new soil in the pot. With other hand, spread-out roots and dibble more soil into all the spaces between the roots. If rootball is too dense to just cover the roots, gently use a chopstick or the back end of a pen to poke soil down between roots until there are no voids. (air) Lightly mist roots with ph'd water to avoid drying out during this process.

Gently tamp the soil surface and water thoroughly. Add more soil as needed to reach base of the 'trunk'. Temporarily stake if necessary.