You can download updated torrents without getting "file too large" error, by following these steps:  
1- Download and install Teracopy or any program that has an option to copy/move files if the size is different.  
2- Start the new (updated) torrent in a new folder.  
3- Stop the new torrent when you are sure that all the files are created (no need to wait for them to be downloaded or allocated).  
4- Close Tixati.  
5- Move all the new folder files at once with Teracopy (or a similar program) to the folder where you have the old torrent files. When you get Destination file already exists, click on More option, applicable to all files, then on replace all files if size is different.  
6- Move all the old folder content to the new folder. This time when asked, click on Overwrite all.  
7- Open Tixati and resume the torrent.

Correction:  
On step 3: Stop the new torrent only after completing the phase of initializing files.  
On step 4: You can just stop the old torrent. No need to close Tixati.

I solved the issue by renaming the file within Tixati files.

1- Stop the transfer
2- Rename the file
3- ForceCheck the file
4- Start the transfer