Externalize or other solution to build dense plots docs on writeLaTeX

TeX capacity exceeded, sorry [buffer size=20000

There are questions about memory exhaustion when building docs with tikz plots in it. I could not find a solution, though.

Downsampling is not an option as the figure is already highly downsampled. It's a 3d plot with lots of lines. There is an answer about increasing mem size and externalization but how to do that on writeLatex? I found this answer about passing command line options:

yes - you can set command options by creating a custom latexmkrc file in a project, with $pdflatex = 'pdflatex --shell-escape';

I tried it to enable externalization, by creating a file with the given single line in the main directory. But how would I name the file latexmkrc or what extension would it have? Maybe it's .latexmkrc but this is not an allowed file extension. Is this a limitation of free accounts (I only have a free one)?

• How to name the file correctly?


• Any other way to build dense plots on writeLatex?