looking very nice.
Have you thought of making a scraper/cleaner for the supported rails carriage?
In the past I have used pot scrubbers ( cheap scotch-brite nock-offs)
the flat ones .. Like these https://www.youtube.com/watch?v=kAv-pKD0Eug
profile to suit the rail section.. Green side out. sandwich between to alu plates.
I soak them in sewing machine oil prior to installation

Paul