How to reduce Excel file size when using PP and PQ?

I am using excel to combine other excel files and to do calculations on them, including average, std, but also more personalised equations (hence PP). Specifically, the purpose is to have "database" because I work with a lot of csv and excle files that I constantly need too extract information from (e.g. 50 files in all of which I only need 2 columns in 4th sheet), pain without PQ.
Currently I am doing "create connection only" when loading queries, and I retrieve them using pivot table with filters, so at no point all of the information is retrieved. I am not sure what else I can do to reduce file size/improve performance. Current file size is about 55Mb, which is a lot.