If none of the above methods can effectively reduce the size of CAD files, you can try the following methods:

1. Compressed file: Using compression software such as WinRAR to compress CAD files can reduce the file size.

2. Delete useless information: use the cleaning tool of CAD to delete useless layers, blocks, styles, etc. To reduce the file size.

3. Reduce redundant points, lines and surfaces: There may be many redundant points, lines and surfaces in CAD files. You can use CAD simplification tools to delete redundant points, lines and planes and reduce the file size.

4. Convert file format: Convert CAD files into other formats, such as DXF and DWG, which can reduce the file size.

5. Split files: divide a large file into several small files, which can be processed separately or reduced in file size.

It should be noted that before any operation, it is best to back up the original file to avoid the loss of the file due to unexpected circumstances.