@Jon @AdventureIslands and anyone else with this issue.
Took some time to take a crack at the issue and here's what I came up with.
iPhone 6 and 6+ use 2X scaling, even though 2X isn't *real* resolution what capturing the screenshot did was take the scene width (Mr Tart for example is 480x320) and multiplied it by the scale. (This would explain why the screenshot was in 16:9 aspect ratio but didn't cover the entire screen). So what I did was grab the *real* resolution from the device to take the screenshot from using openfl.system.Capabilities.getResolutionX and Y.
This Tweet: shows the result captured on iPhone 6+ simulator with Mr Tart in "scale to fit (Fullscreen)" mode.
to install it go to [Your Stencyl Install] > Plaf > haxe > lib > stencyl > 1,00 > com > stencyl > behavior
replace the attached file with the old one located in the above directory.
@Jon or Stencyl team, if you commit this fix could you please replace the how to install with something like "Commited to build"?
Available now in build 8288.
Tested on iPhone 5s, 6+, iPad