Angels & Demons ending: Big Spoilers here

Okay, I just finished Dan Brown’s Angels & Demons. I am about to utterly spoil the ending for anybody reading: you’ve been warned.

I have to know if this ending is as utterly implausible as I think it is. In order for the camerlengo to pull off this stunt, he depends on the presence of a running helicopter in St. Peter’s square. Don’t tell me that he could have pulled this off with the helicopter parked, as you might expect, at the Vatican helipad - Mr. Brown’s handy map shows that at the other end of the Vatican - there’s no way he could have pulled off this stunt in the time he did.

So, the helicopter is there because Max Kohler flies in with mere minutes to go before the bomb goes off.

So my question is - is Kohler’s flight into the Vatican part of the camerlengo’s plan?

If so, it seems utterly unbelievable that this guy would have relied on a crippled scientist in Switzerland being able to see thru his entire plot, then be angry enough to copper into St. Peter’s square with mere minutes on the clock.

If not, then what the heck was his plan to get the bomb out of there? Clearly, he was relying on the helicopter (he stashed the black parachute). Also, he needed someone to kill in order to claim victory over the Illuminati. What was he planning - to kill one of the Swiss Guards (Rocher, Ollivetti?), brand himself, and then make a mad dash to the canister, then to the helipad? WTF- are you kidding me?

And then there’s that mysterious call to Rocher in chapter 99. Who was on the line? We’re led to think it’s Kohler, but if that was part of the camerlengo’s plan, you gotta be kidding me.

Please, somebody tell me I missed something.