Yes, you could try that. They may need to go more laterally across the top of your buttocks. But try that placement first.
About an inch above where the crack ends.

Clean the area off well, soap residue often stays there, and will impede the adhesive.

Sweating also will be problematic. You may have to stick them additionally with plastic surgical tape (available in any pharmacy or WalMart, etc). The tape isn't expensive.

When I had my groin injury...I used them there on the sacral area, mostly on the side where I had the tendon tear. If your backside is really curvy, they stick less well. But that lower back is pretty flat and doesn't make a huge problem. I was upNorth and had little else to use, and these made it bearable (horrible pain for 2 weeks). When I got home I had PT and that helped more.(ultrasound and electrostim). You might consider asking for PT if you find the Lidoderms are helping. The ultrasound was fabulous IMO. The IFc was also helpful.

For curvy spots, I cut them into long strips, and used tape and stuck them on in a row around the curve. That stuck better than one whole patch.

The biggest downside to Lidoderm patches is the poor sticking quality they sometimes have.