Did you also fit the tray before the oil pump?
Haynes suggests sealant on both the sump and crankcase surfaces, with a tray that'd be all 4 surfaces? Overkill?
This is maybe me just being paranoid as it's my first engine build, and i've complicated it by using a Lupo crank sensor, this means i now have a rubber gasket sealing the flywheel end. This makes me think double gasketing is the way to go.