This is a stiuation you cannot win.
As I said before, the flaw in large rendering is NOT that ArchiCAD can only make 4048 pixels of rendering, but that ArchiCAD's texture map surfaces lack the resolution to support such a size.
At large rendering sizes, you need not get very close to a surface before the actual pixels of the texture map start to show up even if the rendering engine is anti-aliasing them into a smeary blur.
This is why we suggest making a smaller rendering and using Photoshoppe's Image Size function to enlarge the image - it will make a view with uniform sharpness that is more pleasing to the eye.
Furthr, from my experience, users are mistaken to think they can make a large rendering on a high-resolution inkjet printer printed huge and still have the kind of detail and resolution they achieve with an 8x10" rendering.
This is not possible. Trying to make a rendering with close-up detail beyond the 8x10" size is disappointing. The ArchiCAD artist can't put enough actual 3D model detail to satisfy the eye - plant surface start to look fake on close up examination. It's a mess.
The way we cope with this when making a poster is to expect the viewer to stand back farther than eye-to-hand distance, like he would for any large artwork - and in that case, the artwork will probably have a resolution of around 50-100 dpi. Think about the equivalent enlargement from a digital camera.
As a counterpoint to excessive pixel neurosis, ArchiCAD users should study the concept of sharpening. Sharpening is a digital process undertaken in Photoshoppe (Unsharp Mask) where, for a specific sized output, the software analyses surfaces and edges for their contrast, and increases the contrast at appropriate places. This function reduces the overall blurring that digital sampling and anti-aliasing induce to give the appearance of incredible sharpness and definition without actually adding detail.
Attached is an example of how a texture becomes over-resolved. From page 110 of my book, it shows how a 20 pixel hole, when rendered at 168 pixels in width becomes smeared and blurry because of anti-aliasing.
Dwight Atkinson