I didn't mean to be the bearer of bad news, sorry!
The weak battery issue is well-known with the DNA75; sadly a single cell, whether 18650 or 26650 struggles to provide 75 watts for long because of battery sag. I think whereas other 75 watt single cell mods 'pretend' to work the Evolv chip actually lets you know that your voltage is sagging below the minimum while you're firing the device.
You might like the VT75 if you're not going to push it past 50 watts, but be careful not to tighten the battery door too much or the c-frame will start developing gaps where it meets the shell. Just screw it in until the battery doesn't rattle anymore and don't go past that.
My other issue with the VT75 is that the removable 510 plate got stuck to my beloved Kayfun 5 and I had to spend hours getting them apart. I don't know why Hcigar decided to make the 510 plate removable but it screws off and might get stuck to your atomizer.
Overall it's a pretty device that let me down. I have the Therion now and I'd pick it over the VT75... sure the Therion would have been better as a DNA133 device but I still think it's the best DNA75 device available now. I think the DNA60 is much better suited to a single battery, and is quite small compared to the 75/200 chip which are the same size.