How to safely downcast USTRUCTs

Unreal Engine supports downcasting of UObject* via Cast<T> and via a custom implementation of dynamic_cast<T*>.

When downcasting USTRUCT objects, both methods don't work:

1. The methods of Cast<T> do not support conversions to UScriptStructs.
2. UE4 compiles without RTTI (e.g. /GR- is set for cl.exe) and UE4 uses the dynamic_cast<T*> of the implementation for pointers to USTRUCTs. Therefore the compiler throws C4541 (see example below).

Is there a method in UE4.22 to safely downcast USTRUCTs using the reflection system of UE4 (so when static_cast<T*> etc is not an option)?

If not, then why UE4 doesn't support downcasting USTRUCTs by its Cast functions? E.g. shouldn't they be referenced or are the reasons Blueprint related?

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Example for (2), use within an UE4 project:

#pragma once
#include "CoreMinimal.h"

USTRUCT()
struct MyStructBase
{
    virtual ~MyStructBase() = default;
};

USTRUCT()
struct MyStructDerived : public MyStructBase
{};

void TestFunc()
{
    auto lvalue = MyStructBase{};
    auto lvaluePtr = &lvalue;
    auto o = dynamic_cast<MyStructDerived*>(lvaluePtr); // cl.exe throws C4541
}