Ok, I've got a double block against the last leader. I'm fairly confident in it, but I don't have the troops yet to test it out.
If anyone's adventurous enough to want to try it out for me and (hopefully) save about 200r, I'd appreciate it. Otherwise I'll edit this post (or remove it) when I've tested it out.
1st, 18r sacrifice on C15.
Don't forget to do this first. Then,
Use 200E block (slow gen) from X5 to C15
Use 180R block (slow gen) from X6 to C16
Use 40R, 70M, 140S from X7 to L17
Launch attacks in quick succession.
As I said, I'm fairly sure it will all work, but I thought I'd better add the disclaimer that haven't tried it and I can't even sim the last guy, so no guarantees.