Upgrading GW 2014 R2 server from OES2015 to OES2018

Have a site that has a small GW system running GW 2014 R2 latest build. One of the server, which happens to be the primary domain and post office, is also running OES2015. Have been in the process of doing in place upgrades of the other OES2015 server to OES2018 no issues. Been holding off on this one since it has the GW component. Going to upgrade the GW to 18 once the migration is done, but in looking at the documentation it appears that for GW2014 R2, OES2018 is not a supported environment. Was looking to see if anyone had done this before successfully. Site does not have space to build a new server to migrate the data off too so kind of stuck with in place upgrade. The second GW server runs a secondary domain, gwia and webaccess and it is straight SuSE11 SP4 so that is a simple SuSE upgrade.