Gzip compression not optimal

Hi,
Great plugin by the way, but the only thing that is raising questions for me is the slightly sub-optimal compression. GTMetrix keeps reporting that compressed assets could still be compressed more, squeezing that extra few percent out of it, and achieving slightly higher scores on the metrics.
Is there any way that the compression algorithms could be tweaked to get the extra few K out of it? Some “other” optimisation plugins require you to purchase the “pro” version in order to enable optimal compression but I know this is not the case with Breeze.

Many thanks,

Anthony