Howdy Franklin,
XML files by nature are going to be large. This is mostly due to the fact that a large number of tags are needed to describe any data. Additionally, the files are saved in ASCII format, making it easy to read in any text editor, but even larger in size.
A solution in this case would be to write your own XML schema which is streamlined for the minimum amount of information and tags needed to describe the data. However, this is a complex solution that would require you to have good knowledge of XML. Also, you would save some space, but the optimized schema still may not fit your size needs.
If size is very important for your reporting needs, you may want to consider using HTML or ASCII reporting as an alternative.
Thanks and have a great day!
Andrew W || Applications Engineer
National Instruments
