Could the filter show real size of source file ?

[vwu00000]

No description provided.

[aleksk]

Are you talking about the file size in Explorer? As far as I remember, it relies on directory enumeration, not on the NtQueryInformationFile, i.e. FindFirstFile/FindNextFile.
You'll need to handle the IRP_MJ_DIRECTORY_CONTROL and fix the sizes there.

Someone can just replace the original file making your local information incorrect. Some systems also return incorrect values if you query remote file info. Do you want to show incorrect file sizes?
I chose not to emulate size to avoid potential confusion, when you open 1KB file, and suddenly see 10MB of data there.