Are you aware that 126.96.36.199 is already capable of accessing large files (i.e. > 2 GB)? I did this modification a year ago because of the 4D features of CARA where spectrum files are becoming really big. The 188.8.131.52 does quite well with 64 Bit file pointers, even if the application itself is 32 Bits. That was not the case in the 1.8.4 version which can only handle 32 Bit file pointers.
I had not tested or looked into large file support, as my problem had nothing to do with file sizes. We observed that CARA's file chooser windows consistently failed to display certain files and directories, often including files and directories that had just been created by CARA itself. This turned out to be related to the fact that the network file system on which the files reside has far more than 5 billion i-nodes, so many of the i-node numbers
are too large for a 32-bit integer. I'll leave out the details of the analysis, but it turns out that whenever 32-bit CARA attempted to get a directory listing, the listing was truncated at the first file whose i-node number was at least 2^32. 64-bit CARA does not exhibit this problem.
Concerning the forum: what file type did you intend to upload? I can add the type to the white list of the forum software, then it should no longer complain.
I didn't see an option to specify a file type myself, but if I recall correctly, the forum software auto-identified it as text/x-patch.