I would use extension tubes, but not reversing.
With a film camera, no problem.

But with a digital camera, dust is the enemy.
It's expensive (usually) to get the camera sensor cleaned.
And reversing the lens so it gets dust all over it, then possibly putting all that dust inside the camera does not seem like a good thing.

Extension tubes are relatively cheap, and as long as you can stand the long exposure or use lots of extra light, you can keep on adding them.

I once made up a two foot extension tube for my old film camera and got some great images at about 7:1 magnification. But I had to fire the flash about 5 times at a distance of 6" to get enough light on it. I think it worked out at about f/140 or so.
Again I wouldn't do that for digital because of the possibility of dust.
Sometimes film cameras, where you can easily clean everything, are the best tool.