Not to put you on the spot, but more to clarify and correct any typos etc
- should someone want take your build data at face value - you might want to double check those numbers, Rhyno. The math doesn't work out to 0.5Ω, for the specs stated.
Per SE
* - dual parallel coils @ 8 wraps (7.59) of 28 gauge Kanthal A1, with a 3mm mandrel (combined leg length calculated at a typical 8mm net)... would provide a net resistance of 0.85Ω.
You'd need 5 wraps (4.67) for a 0.55Ω net resistance, or... your 8 wraps - but on a 1.5mm mandrel.
"Thoughts?" Running at 80 watts, your "heat flux"
* (for 28 gauge 0.85Ω duals) is a
very warm 418 mW/mm
2. Even hotter at your stated 0.5Ω
target resistance... 710 mW/mm
2. "Heat Capacity"
* and "Coil Leg Power Loss"
* (for 0.85Ω) are OK at 25 mJ/K and 8.4%, respective.
As a point of reference and perspective... an unregulated 18650 mech (@ 4.2v) will discharge 35 watts 8.4 amps to a 0.5Ω DPC build, for a warm HF of 311 mW/mm
2.
*If you've an interest in learning more about the terms mentioned above... click the first two hyperlink/siglines below.
Cheers