I would say a softer washer (nylon,rubber,plastic) will do the trick. Something that compresses slightly easier than copper to create a better seal. Then if that works, get a fumoto, or autozone actually has some for $12.99 but by a different manufacturer.

On the other hand, unbolting the crossmember does not seem to difficult and from the looks of it, that is all at most that would need to be done to get that pan off. I give this opinion becuase I almost dropped my pan last oil change just to re-seal it and clean off some gunk that resides around the front bolts on the pan.