Thanks UCyborg, works fine but if you pin Chrome to the Classic Shell task bar once started and then use use the pinned Chrome, the transparency doesn't work (it did using the previous method) !
Managed to fix this by right clicking on the taskbar pinned Chrome and then right clicking on Google Chrome on the pop up menu. Select "properties" on the new pop up menu and reedit the "Target" to append "--disable-features=Windows10CustomTitlebar"