2011 Versa Rear Suspension Help

[kenxq5471]

This isn't the typical post on this forum. My parents have a 2011 Versa. My mother requires a mobility chair. I bought a frame hitch and motorized lift for the back of the car to help her get around a bit better. When the chair is on the lift it adds 300lbs behind the rear bumper. You guessed it, and I was afraid of this, the car kind of rides low. I have read all kind of posts on here before posting and cannot find anything. I am looking for advise on how to beef up the rear suspension while not giving it a rough ride when not loaded.
Took it into a mechanic and he said there was nothing I could do that wouldn't make it a rough ride. Does anyone have any suggestions? I was wondering about air bags.

[Promise Land]

I would search the airbag route due to you want two different riding / support types when the chair is in or out of the car. Helper springs are only going to make it ride harsh without the chair.

[kenxq5471]

Thanks for the advice. Does anyone know a particular type of airbag system to buy, that won't cost me an arm and a leg. Already have $1,500 in this project and it is basically a gift.

Thanks Again

[Promise Land]

Google turns up a few results. I'd try looking through the results to see what would work for the weight the chair adds to the car.