Hello grauzone,
You shouldn't cast structs or any other types to ubyte[], because the memory representation of those type is highly platform specific. Structs can contain padding, integers are endian dependend... If you want to convert these to binary data, write a marshaller. You _never_ want to do direct casts, because they're simply unportable. If you do the cast, you have to know what you're doing.
Never say never. Some cases like tmp files or whatnot where the same exe will save and load the file never* have any need for potability.
*"never" uses intentionally :b.
