First, get a second opinion. In my case, I'd suggest go out and crawl under the vehicle. Over the axle is a rubber bumper, between the axle and the frame. There should be an inch or more of air space between the bumper and the axle. At least that's my memory of the matter.
More importantly, does the vehicle go thump when you go over a bump? Does the hump thump when you go over a bump, lump lump? Does the hump thump you in the rump, when you go over a bump, lump, lump? If so, you may have a wump. A wump in your trunk could be very sad, and bad. You brother may be a frump and you may have been had. This, I learned from my Dad. My Dad's wump was neat the back bump, and it would thump when he drove the trunk over a hump, lump, lump.
I got a set of helper springs one time at an auto parts place for $25 or so.
JC Whitney has this kind of thing advertised, but the couple times I bought there, the customer service was terrible. They sent me the wrong parts, I wrote to tell em what happened. They sent me a Toyota adaptor for a battery separator, when I wanted a battery separator. They refused to send me the part I wanted, even though I mailed em a photo copy of their own catalog, with the part that was missing slathered in yellow Hi-Liter. But, I'm rambling.
The helper springs went in, about an hour work. Is Dr. Seuss going to reach out of the monitor and lump me for stealing his lines? I'll be downstairs hiding in the sump.
If the only thing bothering you is your brother's advice, ignore it. If the vehicle bottoms out on bumps, consider he very slightly might be right.