My first mech mod was a cheap clone picked up at the local B&M. It couldn't handle low-ohm builds - would heat up like crazy at 0.3 or below. Button got too hot to touch.
I re-wound the spring in the button using copper wire that I removed from an old piece of coax laying around in the garage. That helped quite a bit. It got a little warm, but not that insane level where I had to set it aside for 20-30 min to cool down. With a multimeter, I found that the resistance in the original button was greater than the resistance in the build, so the heat built up in the button and not in the coil. This led me to making a new spring for the firing button.
I eventually (after 4-6 weeks of use) junked that hunk of metal, and got an IPV3. I prefer regulated - and a good mech mod isn't cheap - more expensive than an IPV3.