Not yet. Temperatures wont go below 2 C (during the night) the coming two weeks.
What I read thus far is that getting roots is not the main problem,
but that the root system is most often to weak to sustain the tree. Any thought on that?
Unfortunately there is no room left in my backyard.. (a relatively small back yard, 80m2, is one of the reasons in got into bonsai).
Peter Chan doesn't think also (Bonsai From Field Grown Material). The way he works the roots of a large maple!
i was thinking when i saw the roots, why do you want to bother layering off the base after youve just dug it up, doesnt make sense to me, if thats the case then why even bother digging it up in the first place. just pass on it.
i think the base is fine, there is some flare and balance there, thats all you need. not every tree has to have a perfectly manicured finely tuned, radial nebari.
and yes look at the one Peter chan just worked on for reference, that maple will be worth a fair bit of coin once its refined.
you got a large amount of root, the tree should be fine, if you have a container that will accommodate all that root then great.
are dissectum a good variety for bonsai though, seen any good examples? whenever i see them at the nurseries or garden centres i tend to pass them up. same with bloodgood or variegated maples, just not the ones i tend to mess with.