Josh, I haven't run through your numbers, but I can tell you that yes it does work, and it's even better when they offer money back on 2-3-4.

After running through your example I come up with the following.

Wins = +70, and -67 and -4 the place, = -1.
Places = -50 (+50), and +44 and -4, = +40.
Unplaced = -50, and +44 and +13, = +7.

There are ways to make it risk free, and if you lay the win shorter than you back, then there's no need to lay the place.