Second, I went from 5.1 FR4 to 5.2.CR1 on a SMEG+ unit. So, the only file I have used is a 5.2.CR1 I found elsewhere. I did some research on the respective file you linked to, and I discovered that the length of the binaries contained appears to be different from the length my file has. The number of files and folders is equal, though.
The file I used worked OK, so I decided to put my file on mega so you (and anybody else who is quick enough) may download it.
But, remember: Don't use this file unless you upgrade to a 5.x firmware beforehand! This firmware is only good for SMEG+ units
Vital stats of the file are:
153 files contained in the archive.
length: 1.191.365.312 bytes
packed: 1.129.257.019 bytes
SHA-1 hash: CB3820F45FDFA7298088BDC6B458C30C6C6EABA5
The file has been rared with Winrar Version 5!
link: [Only registered and activated users can see links. ]