Thanks jensmander,
So I am using 5.1-5022 and I can see it went as high as 5055. Would I follow the same instructions you just gave me, find expenoboot for 5055 and patch it manually before then moving to to 6.2?
According to this site, https://www.synology.com/en-global/support/download/DS3615xs#firmware, I can jump straight to 5.2-5967, then 6.0.3-8754 and finally to 6.2.
Thanks again!