This actually seems to work. I had a coin fail first, but second time around, here it is:
I tried applying the same theory to getting the Lighthouse dragon, but after three tries and fails, it was too expensive to continue. At least I only got maps once, but I got orbs, too, and I have no use for those. I could afford one more try, but I'd rather keep some gold in reserve for speeding things up if needs be.