Three days mid week is a tricky proposition as there are not really any coupons or offers available. Most three day offers require a weekend to be included. Most likely you would be able to get a better deal if you could keep the car five days (found a $134.81 compact on Alamo.com including taxes and fees using contract ID 7013604 and coupon ID AD3829MRB).

If that is not possible I would test out some contract ID's. Here is a link to a good list:

http://www.fatwallet.com/t/63/521905/