Sliced a breadboard down the middle for my ESP32 and it works great

Ran into the same wall last year with a Wemos-based ESP32 clone I got for a humidity monitor project. Even with the board sitting on the very edge of a standard 830-point board, I could only reach one column per pin, and I kept pulling rows loose every time I bumped a wire. Instead of cutting anything, I ended up buying two of the little 170-point mini boards for a couple bucks each. Clipped the positive and negative rails off one end of each so they were independent, then sat them on a piece of MDF with about a finger-width of space between the two inner edges. The dev board spans that gap and every pin lands in its own row. A dab of hot glue underneath keeps the spacing from drifting.

The tradeoff is no long continuous rail down the middle, so if I need extra ground points I just run a short jumper between the two mini boards. For small sensor hookup work it has honestly been plenty. Yours is the better route if you want the full length rails though, since my little boards only have a couple rows of usable columns on each side of the chip. One thing I learned the messy way is to plug the board in and mark where the pins land before fixing the spacing down. I glued my first set up a millimeter too narrow and had to pry it apart with a butter knife, bending two pin headers in the process.

I did something similar but lazier. Instead of cutting one board, I pushed two of those cheap 400-point boards togather side by side on a piece of scrap plywood and hot glued them down. The gap where the two plastic bodies meet ends up a lot wider than a single board's center channel, so my ESP32 dropped right in with pins on usable rows both sides. Cost me nothing extra because I allready had a drawer full of partial boards from old kits.

The bonus is you can pull one half away if a project outgrows the layout, or slide the whole thing apart when you want to work on a smaller board. Downside is the power rails don't line up across the seam like they do on one continuous board, so I run a couple of jumpers between the rails and stop thinking about it.

Only warning I'd add is watch the glue line thickness. I used too big a dab under one side the first time and the two halves sat at slightly diffrent heights, which made a few pins sit half-in their holes. Peeled it off, redid it thin, been solid for months. For anybody getting a fresh dev board anyway, some of the narrower ESP32 clones only cover one column per side, but I had already bought mine so the two-board trick was the free fix for me.

I ran into a similar problem just trying to get a simple voltage reading on the power rails. Even when I managed to get the board sitting right in the modified gap, some of the pins were hard to see with the regular screwdriver. I had to use a toothpick and try to wiggle the wires a bit to make sure the connection was solid. Do you think the pins along the very outer edge of the ESP32 are more prone to loose contact than the ones right next to the chip?

I tried modifying my board for a similar project. Once I got the DevKit seated in the custom gap, I noticed the voltage on the 3.3V rails seemed to drop just a bit compared to the power jack on the left. It's strange becuase I'm only using a low-power sensor, but I wonder if splitting the board causes some wierd power distribution issues across the rows? Has anyone else seen a voltage drop like that?

All those plastic fixes are a mess when you think about it. When I was first working with these chip prototypes back when the headers were just raw pins, we skipped the breadboard entirely for the final layout. Those DevKit boards are just too big and awkward for what is really simple sensor wiring. You can spend time cutting plastic, but if you are going to make something reliable, you shold be jumping straight to a small strip of perf board. Just run a few short header wires and solder them down. It’s more work upfront, sure, but you don't end up with those flimsy, half-cut plastics that rattle when someone bumps the bench. A solid connection is worth the extra five minutes.

Update: tried the two small boards glued to a scrap of wood like the second reply suggested, way cleaner than my taped hack, so that one's going permanent. Also that voltage sag on the 3.3V rail someone mentioned got me wondering. I checked mine with a meter and there is a slight dip when the sensor's plugged in. Could the rough cut edges be giving a marginal contact? Gonna clean them up with fine sandpaper and retest.