Is this the right way to implement pimpl wth unique_ptr and move-semantics in C++11

I haven't yet seen a pimpl example that utilizes both unique_ptr and move-semantics.

I want to add a CHelper class to STL derived containers and use pimpl to hide what CHelper does.

Does this look right?

Derived.h

class CDerived : public set<CSomeSharedPtr>, public CHelper  
{
//...
};

`

Helper.h

// derived containers need to support both copy and move, so CHelper does too  

class CHelper  
{  
private:  
    class impl;  
    unique_ptr<impl> pimpl;  

public:  
//--- default: need both cotr & cotr (complete class) in order to use unique_ptr<impl>  
    CHelper();  
    ~CHelper();  

//--- copy  
    CHelper(const CHelper &src);         //copy constructor  
    CHelper& operator=(const CHelper &src);//assignment operator  

//--- move  
    CHelper(CHelper &&src);         //move constructor  
    CHelper& operator=(CHelper &&src);//move operator  

//--- expose public methods here  
    void SetModified(BOOL bSet=TRUE);  
};  

Helper.cpp

//===========================  
class CHelper::impl  
{  
public:  
BOOL m_bModified; //has the container been modified (needs to be saved)  
// ... other data  

impl() {m_bModified = FALSE;}  

//--- copy cotr/assign  
impl(const impl &src)  
{  
  *this = src;  
}  

void operator=(const impl &src)   
{  
  m_bModified = src.m_bModified;  
  // ...other data  
}  

//--- move cotr/assign ?? do I need to write move cotr/assign ??   

};  

//============================  
CHelper::CHelper() : pimpl(unique_ptr<impl>(new impl())) {}

CHelper::~CHelper() {}  

//--- copy  
CHelper::CHelper(const CHelper &src)  
: pimpl(unique_ptr<impl>(new impl(*src.pimpl))) {}

CHelper& CHelper::operator=(const CHelper &src)  
{  
  if (this != &src)  
    *pimpl = *src.pimpl;  

  return *this;  
}  

//--- move  
CHelper::CHelper(CH