@rhubroma - I think you're misguided in thinking that there is a formula to doing the double that means you can turn up at the Giro and the Tour in perfect form, the same form as if you'd just targeted one or the other. Perhaps it was possible in the 90s, but that's a different era when being skeletal was not a pivotal factor.
Losing that last KG that makes the difference between being skinny and being skeletal must be extremely difficult and require intense training and a very controlled diet. This is the exact opposite of what Contador needed after the Giro, he needed rest and to eat healthily so that his body could repair itself.
In my opinion, there just isn't enough time between the Giro and the Tour to both recover and train at the intensity required to get to Froome level of fitness (esp. weight-wise). At the same time, I don't think it was an option to go into the Giro in peak form/weight and try to more or less hold it for the Tour - I mentioned before that I think he'd almost certainly get sick or injured being at such a low weight for so long, besides even considering the fact that he'd probably fade in the Tour. form-wise
At the beginning of the Tour, Tinkov commented that "it isn't fair that Contador is racing against guys that are fresh" before going on to say he still believes in Contador in a subdued manner. Throw-away comment? Personally, I read quite a lot into this and I believe that Contador and his team knew it just wasn't physically possible to be at 100% in the Tour and his training data leading up to the Tour showed that.
This doesn't mean he has no chance - I still believe he's in pretty good form and perhaps peak form will come in the 3rd week, maybe Froome will fade, maybe he can benefit from playing the stronger guys off against each other or other tactics.
Whilst Basso's attempts in 2005 and 2006 must provide useful data, we also have to remember they were both ultimately unsuccessful attempts. In 2005 he bonked heavily in the Giro at an early stage and was able to rest-up for all except one stage of the remainder of the race. In 2006 we just don't know what Basso would have done at the Tour - it seems to me that Basso peaked for the Giro and just hoped for the best at the Tour. But even in 05/06 I believe that illicit methods of recovery were available that are far more difficult today (I don't mean to imply they're saints today, but times have changed in terms of what you can and can't get away with).
One other thing to bear in mind when comparing this double attempt to Indurain and Pantani. Indurain and Pantani were head and shoulders above everyone else in their respective disciplines of TTing and climbing. They didn't need to be at 100% to still be the best at those disciplines. In particular, I've noticed that good TTers are often able to put in a good TT even when the form isn't great. Ullrich in the '06 Giro is a good example of that. On the other hand, I don't think Contador has ever been head and shoulders above his competition at either TTing or climbing. It's just that he's been one of the best at both and is sublime at eeking out a win one way or t'other.