I've been using a nice app I found for my
coils and it's drastically improved my flavor! It's available for iPhone. It's called MicroCoilPro on the app store. It cost me $4.99 but was totally worth it in my opinion. I'm not affiliated with them at all, I just saw a youtuber talking about it and gave it a try and really liked it.
The app not only shows ohms, amps, and watts, but it also shows the heat factor (W/mm2) which I think is the biggest way to find the sweet spot of a coil.
By plugging in your info (1/16, 28 gauge Kanthal, and 8 wraps) it shows your heat factor at .31 W/mm2 which is in the orange at 4.2 volts (Medium taste, medium vapor, and slow responsiveness). Your build does, however, go into the green (Dense vapor, Taste in the sweet spot, and swift responsiveness) after the battery volts drop off a bit.
By adding an additional coil (9 wraps), the heat factor goes to .25 W/mm2 which is in the green between 3.7-4.2 volts. You would be around 1.11 ohms at 9 wraps. Try that and see if it helps. I don't know much of the science behind all of this, I just plug in the numbers and go by what it tells me. I hope it helps you. Let me know!