Reduce the number of extensions, galleries, templates, etc., to start. You might need to do this by "removing" the associated ".deb" or ".rpm" files in the installs. But you need to be careful not to remove needed items. Remove any language pack that you do not need. Remove any other item that ends up in the extension manager list that you do not need. The "locked" ones can be "removed" by not installing them. Do not install the help pack. Do a full purge of LO and then do the install so there are not any files that are carried over from the previous versions. Delete LO's old config files before the new version.
The real question I have is why do you want or need to limit LO's install size?
Do you have a limited drive space?
I have installed packages on Windows that take up 1 or 2 GIG for the install space, so 400+/- is not bad for an office suite.