EdgeMTB Display Value Understanding

Hey (again),

I've had some end-user feedback that the image I get from a web request (PNG) display received on the EdgeMTB device is substandard.

The user sent some screen shots (captured from device) that are an absolute dogs dinner!  The device list (https://developer.garmin.com/connect-iq/compatible-devices/) just says this is a High Colour so I went into the "compiler.json" files at the SDK install folders Garmin\ConnectIQ\Devices\

The EdgeMTB reports differently to the other Edge 1040/1050 series devices in the following ways:

    "alphaBlendingSupport": false     [this is true for other Edge]

    "bitsPerPixel": 16                            [this is the same as other Edge]

    "outputColorSpace": "ARGB2222"    [this is missing for other Edge]

    "imageFormats: [ "png", "jpg" ]             [this is missing for EdgeMTB but present for other Edge]


Whilst the simulator is not an emulator, my graphics look great there and so without the EdgeMTB hardware can anyone hint at how I need to alter my return images that I though would be OK as I naively expected the same screen tech and bitsPerPixel would mean similar image support.

Does all this simply mean I need to ensure there is no alpha / transparency in the image?
Can I do that in the makeImageRequest() options parameter as a transform or palette?

If I could replicate the quality issue on the simulator I could make changes and see the results, but at present I feel I'm flying blind a little.

 Many thanks in advance