I actually had good luck with the ipv4, UNTIL I had a different issue. When firing the mod and using dual claptons @ .35 ohms, the resistance reading would change while firing, rapidly changing the voltage. Was going to toss it, threw it on the shelf unpowered for a while, came back to it, and mysteriously it started working fine again. Think it's great while it's working, but not sure if on borrowed time or not. Picked up a 5 which is working fine, but liked the 4 better.
Firmware is a good idea.