Hertz - FRDM AND Upgrade? Possible?

I am trying to book a reservation at MCO and can't seem to get both the FRDM rates (every other rate is $40+/day, FRDM is $20/day) and an upgrade coupon to combine...is this possible? I am getting charged for 4 days, when I am picking up the car at 8PM on Sat, and returning it at 9AM on Tues...and this is KILLING my expense budget...the days I am working with are 10/8 thru 10/12, and I need any car with Neverlost...can anyone help?

I've never used an upgrade PC with the FRDM rate, but it has worked with dollar-off, free day, and points/miles PCs.