Taiwan Maple Root Over Rock advice

[Thymetraveller]

I picked up this little potfull at Bonsai Art in Terrey Hills a while ago.

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It's 5 little Acer buergerianum var. formosanum fused solidly together at the base making a really interesting clump.

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My plan is to grow it over the rock in the first picture, as in this sketch;

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So...is this going to be possible?

If so, when should I attack? Should I Simply bind the roots to the rock and plant it back at the original soil line in a big pot, or should I be wrapping it in plastic or aluminium foil and establishing a new soil line at the base of the rock?
How long should I leave the rock buried/wrapped before exposing it to the air?
There is a lot if contradictory stuff on the web, and it would be great to hear from anyone who has experience with this technique!
Thanks in advance,

Gareth

[shibui]

You can see my technique for root over rock tridents on Shibui Bonsai site. I use aluminium foil because trident roots are very strong and grow lateral so when you put a root over rock in the ground or a grow pot new roots will grow at ground level and head out. They grow at the expense of the ones clasping the rock an usually ruin your composition. Foil means the roots cannot escape. They must follow the contours of the rock which is where you want them, even new ones that form while your tree is developing.
Plant it so the soil is up to the base of the trunk. The weight of the soil will help push the roots against the rock.
Dig, unwrap and check the root position after 1 year in case some need to be repositioned. After a couple of years you will not be able to make adjustments. Rewrap and repeat if the trunks and roots are not ready.
When trunks are close to desired size unwrap and plant at the finished height. There's no need to slowly expose trident roots.

Note that it is difficult to develop branches while trees are growing fast. Just let the shoots grow freely and then cut back to desirable trunks then make new branches from the shoots that sprout after hard pruning.

Now my opinion on 2 things:
1. I find Taiwan maple does not ramify as well as standard trident. Hard to achieve a nice twiggy branching.
2. The rock you have chosen looks a little uninteresting. I'd take some time to search for a rock with more character.

[Thymetraveller]

Thank you for the swift and detailed reply!
That's an amazing website you have there....I'll be spending a lot of time on it.
I think I'm all set for the end of winter now.
As to the rock; when I open my front door I am greeted by graceful redgums clinging on smooth sandstone boulders, and it is this scene tha has inspired the combination. I'm thinking of a shallow, yellow, oval pot as a complement. Rest assured I'll be venturing into crinklier stones with other trees!
I hear you about the Taiwan maples too, but I just love their leaves
Thanks again for all the wisdom!!!