I would adopt alternative tactics if i am the DS at MS - I will keep the break in check and try to grab bonus seconds at the first intermediate sprint after 64 kms which could give Impey a lead of 5 seconds over Porte - Then I'd let the break go, hoping they will mop up intermediate seconds at 106 kms, and even let the break go to the finish - Then back Impey to finish within 5 seconds of Porte on Willunga Hill - Then it's up to Trek to ride and bring back the break.