@Stigmata You can try the file 'biker Mike XT-6.kmtf' which i added to this post, the route indicator is smaller than the original one! For explanation: This are so-called 'Theme' files and with them, you can change the look of the map on your Zumo XT. They should be copied to the internal storage of your Zumo XT into the folder 'Themes/Map' - please unpack the added file 'biker Mike XT-6.zip', this should give above mentioned theme file and copy it to the described path on your Zumo XT.
This themes are simple xml-files with parameters, which can be changed to make a different look for just anything shown on the map screen - you can take a look at this page here
https://www.javawa.nl/zumocolors.html, where you can upload a .kmtf (Theme) file and make modifications by yourself. I include also a pdf (sorry, only in german) which describes the parameters for the .ktmf files.
There's also Windows program to edit these files - you can get it here:
http://www.pinns.co.uk/osm/theme_editor.html
Hope this helps and greetings from Vienna, Austria!
Bye, Robert

(Actual: Tiger 800 XRx (2016), Garmin zumo XT, Cardo PackTalk, Nolan N70-2GT)