Can a candidate make negative requests from a Super PAC? Restricting their activities? Or is that considered "coordination" and therefore illegal?

Per the Citizens United decision, candidates and Super PACs are not supposed to "coordinate," thus preventing quid pro quo (at least in the minds of five justices). A candidate can't solicit a 10 million dollar donation to their super PAC because then they would be indebted to the donor, but the decision permits the donor to spend 10 million on the candidates behalf without their solicitation.

That in mind, would a candidate be legally permitted to request a Super PAC not to take some action which could be perceived as corrupt? Could Clinton request her Super PAC refuse donations from Industry/Corporation X? If George Soros decided to form Feel the Bern PAC, could Sanders legally ask him to cease and desist? Would those be considered illegal "coordination"?