We rented a compact car at the Kona airport. We got a great rate and the car was fine. I have no problem with the company but thought I would point out what seemed to be a way of trying to get you to upgrade.
My husband is 6'5". When the person helping us saw that he said they were having a special on mid-size cars that we might want to upgrade to so he would be more comfortable. We declined. He then said that after we got in the car if we wanted to upgrade just come back in and they could do it.
When my husband went to get into the car the seat was pulled all the way forward, the wheel tilted all the way down and the seat raised as high as it would go. Needless to say he could barely get into the car, much less drive it! So he moved the seat back as far as it would go, raised the wheel up and we had to look in the cars' manual to find the button to lower the seat. After all of those were adjusted he could fit into the car. We are thinking that by leaving the car adjusted like that, they may just get some people who will upgrade. It wasn't the most comfortable car but for a rental for a few days it served our purpose and we saved over $100 by not up-grading.