Just so you know man, I just installed your image on ESXi 6.5U1, latest build.
It has worked flawlessly (dsm 6.1.3-15152 update 1with Hardware version 13).
And, it has also been possible to upgrade to the last .pat file from Synology at this time (DSM_DS3615xs_15217).
Which means, I'm runing now DSM 6.1.4-15217 Update 1v
I thought it would have been complicated and painfull ot install, but you made it too easy.
In a way, it's a pitty to not have to struggle with it.
Thanks a lot, man.