The following code at line 275 in fs/nfsd/export.c prevents ncp file
systems from being rexported. Maybe the old --re-export option needs
adding?

	if (!(inode->i_sb->s_type->fs_flags & FS_REQUIRES_DEV) ||
	    inode->i_sb->s_op->read_inode == NULL) {
		dprintk("exp_export: export of invalid fs type.\n");
		goto finish;
	}

(Its the FS_REQUIRES_DEV that does it - ncpfs has this flag set to 0).

For now I've just commented it out.