Does anyone else gets bad results with "superSize" in Application.CaptureScreenshot()?

I need to make High-Res screenhots for print. Ideally they should be about 10000 px wide, but I just make them as big as possible.

I use a huge rendertexture which I write to png, but my pc can't handle bigger than 6000x3375. (Drivers crash when trying bigger). Now I tried Application.CaptureScreenshot() (with the superSize parameter) when it was first added in Unity, but the results where never good. I tried it again recently, but it's just as bad as it was (and it takes ages to render).

the bad results I'm talking about are:

• shadows aren't upscaled, so if you set supperSize to 5, the shadow will be squares of 5x5 px.

• skyboxes arent upscaled properly: no filtering, they're upscaled as squares (like the shadows).

• lens flares aren't upscaled properly (like the skyboxes).

• Anti-aliassing doesn't work: looks like multiple images overlayed with offsets, looks horrible.

Does anyone else have these problems?

I find it strange that I can't seem to find anything about this, or am I just the only one trying to render giant screenshots?

I'm using Deferred Rendering btw