I assume you have now made/had made your oil hoses, that being the case you can file a flat on the corner that hits the filter, another option is to get some/a different connector that has a collar section first 1" or so, so the hex tightening bit is further up/away from the sandwich plate.
Failing that you can always use a double female adaptor to move it away a bit, this will have a much much smaller hex around the centre.
They're(sandwich plates) not very well thought out at all really are they!!
tabetha