is it safe to cast interior_ptr and interior_ptr to interior_ptr ?

Is that code safe ? (GetInterior_ptr)

using namespace System;

ref struct A {
	String ^s;
	Object ^o;
};

interior_ptr<Int32> GetInterior_ptr(A ^a) {
	interior_ptr<String^> ip = &a->s;
	return (interior_ptr<Int32>)ip;
}

void *getAdr(interior_ptr<Int32> ip) {
	pin_ptr<Int32> pi = ip;
	return pi;
}

void *getAdr(A ^a) {
	return *(void**)&a;
}

void callGC() {
	GC::Collect();
	GC::WaitForPendingFinalizers();
}

void TestInterior_ptr() {
	A ^a = gcnew A(); a->s = "hello"; a->o = gcnew cli::array<Int32>(20000);
	interior_ptr<Int32> ip = GetInterior_ptr(a);
	void *old_ip_adr = getAdr(ip);
	void *old_a_adr = getAdr(a);
	callGC();
	void *new_ip_adr = getAdr(ip);
	void *new_a_adr = getAdr(a);

	bool ip_adr_Changed = new_ip_adr != old_ip_adr;
	bool a_adr_Changed = new_a_adr != old_a_adr;

	interior_ptr<String^> ip2 = (interior_ptr<String^>)ip;
	*ip2 += "world";

	if (ip_adr_Changed && a_adr_Changed) {
		Console::WriteLine("cool address changed and nothing crashed");
	}
	else if (ip_adr_Changed || a_adr_Changed) {
		throw gcnew Exception("very bad : should crash");
	}
}

int main(array<System::String ^> ^args)
{
	while(1) TestInterior_ptr();
        return 0;
}

the breakpoint I set on 

if (...) {
   Console::WriteLine("cool address changed and nothing crashed");
}

is trigerred and nothing crashes so I guess that means it's safe to cast interior_ptr<X> to  interior_ptr<Y> as far as you don't access to it with the wrong type.

Thank you for your opinion.