Buddy - I just upgraded from 16.1 to 18 before the holidays.  I had 16.1 on a 2008R2 server. With 2008R2 EOL in January 2020, I suggest that you create a new 2016 server & migrate from 16.1 to 18.  That way you'll kill two birds w/ one stone.  The migration was straight forward & I did not run into any issues. (The migration also copies your data.  It does not move the data).  I followed the instructions in this document:  https://support.na.sage.com/selfservice/viewdocument.do?noCount=true&externalId=https--cdnnasagecom-docs-en-customer-300cre-18_1-open-UserGuidepdf&sliceId=pdfPage_23&isLoadPublishedVer=&docType=kc&docTypeID=DT_DOCUMENT_1&stateId=1016&cmd=displayKC&dialogID=30843&ViewedDocsListHelper=com.kanisa.apps.common.BaseViewedDocsListHelperImpl&openedFromSearchResults=true 

That was my experience upgrading to 18.  

Thank you for sharing your experience, that's is the input we are looking for.