Is it possible to have a std::vector of struct with a fexible array member?

I have a struct with a flexible array member that I need to use.

struct Record
{
     uint32_t length;
     Data contents[];
};

I'm able to initialize this and use it by doing something like this: (it would also work with malloc or any other dynamic allocation)

vector<Data> members;
vector<uint8_t> buffer;
Record myRecord;
buffer.resize(sizeof(Record) + members.size() * sizeof(Data));
myRecord = *(reinterpret_cast<Record*>(buffer.data());
myRecord.length = static_cast<uint32_t>(members.size());
// copy members to myRecord.contents

That works just fine. But now I need to have an interface that operates on batches of Record, and I have been trying to use an std::vector for this. Then problems start appearing, and I'm guessing it's because std::vector arranges all elements contiguously on memory, and since sizeof(Record) won't take into account the size of the contents (each vector element will hold only 4 bytes, instead of 4 bytes + size_of_contents * sizeof(Data)), the vector elements are actually sharing memory and then each element starts overwriting the contents of the previous element. Does that make sense?

If this really is the problem, I was wondering if there's any way to "force" the vector to allocate a specific size for each element (instead of whatever sizeof returns for the element's type). That way I could make sure that each vector element would have enough size. If that's not possible, is there an alternative solution? Maybe a different container that would allow me to do so? Please keep in mind that I do need to use the struct as it's defined (I would love to just replace the whole thing for a vector but unfortunately that's not possible)