RESERVATIONS - Having two reservations, one full - with skip the counter and one mid-suv - without skip the counter, but all other details including additional drivers on the Alamo website - so no credit card on file.
Go to the garage and see what is in the full size aisle. Many times there will be suvs and mini vans in the full size aisle.
If you get what you want in the full size aisle, cancel the mid-suv on your phone from the garage. If not, use your phone to complete the skip the line process for the mid-suv. There is an option to print the bar code that you need for check out (which obviously you can't do) . They also email ,almost instantly the confirmation with the bar-code. Now cancel the full size reservation from your phone.
CHECK OUT - At the exit, simply handed over your phone with the emailed bar-code, credit card and driver's license and they handle everything. You are set to go.