Ayinger Doppelbock Clone

[Full Mental Jakey]

Ayinger Celebrator Doppelbock knocked my socks off when I first tried it, and I'd love to make something that comes close! However, my experience brewing dark lagers is very limited, so I'd welcome comments on the following recipe.

Firstly, the Ayinger website has a little bit of information (http://en.ayinger-bier.de/?pid=118). The alcohol content is 6.7% and the OG is 18.5 degrees plato (1076). So I think that infers an OG of 1076, FG of 1026, attenuation of 66%. My 1st thought is, won't that taste a bit sweet in a lager? Anyway, it appears that WLP833 is the Ayinger strain, so that makes yeast choice easy. Lastly, what grain bill to use? There are a few clone recipes on the homebrewtalk forums, with reasonably complicated grain bills. But I often find great beers are made with relatively simple grain bills, and I'd read a few comments that suggest Celebrator could be make with 100% Munich II. Could that be right, it doesn't seem to give a dark enough beer (although a decoction mash and extended boil will make it darker).

From the above, this is my starting point. Really unsure about the grain bill, so please feel free to make suggestions!

Doppelbock
Recipe Specs
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Batch Size (L): 23.0
Total Grain (kg): 7.000
Total Hops (g): 35.00
Original Gravity (OG): 1.077 (°P): 18.7
Final Gravity (FG): 1.026 (°P): 6.6
Alcohol by Volume (ABV): 6.66 %
Colour (SRM): 12.3 (EBC): 24.2
Bitterness (IBU): 21.6 (Average)
Brewhouse Efficiency (%): 80
Boil Time (Minutes): 90

Grain Bill
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7.000 kg Munich II (100%)

Hop Bill
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35.0 g Hallertau Mittlefrueh Leaf (6.3% Alpha) @ 90 Minutes (Boil) (1.5 g/L)

Misc Bill
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Decoction mash.
Fermented at 10°C with WLP833 - German Bock Lager