Dual-core wands?

[Lee Kaiwen]

No: HPFGUIDX 181507

As I was reviewing DH Chap. 23, "Malfoy Manor" recently this leapt out 
at me:

"As Ron ran to pull Hermione out of the wreckage, Harry took the chance: 
He leapt over an armchair and wrested the three wands from Draco's grip, 
pointed all of them at Grayback, and yelled, "Stupefy!" The werewolf was 
lifted off his feet by the triple spell, flew up to the ceiling and then 
smashed to the ground."

The implication of the passage is that casting a spell while holding 
three wands triples the spell's power. But then why isn't every wizard 
beating a path to Ollivander's to pick up a couple of extra wands and a 
tube of superglue?

Or perhaps, since the power of a wand derives from its core, Ollivander 
should start making dual-core wands. Imagine (with apologies to Intel) 
the all-new Phoenix Core Duo - same slim design, double the casting power.

CJ