Depending on what your actual goal is when exporting, there are a couple of options;
Export as Sphere Image - Will export the entire world in Equirectangular format with (base on my experimentation) a max resolution of about 12000 x 6000
Export as Multiple Files - If you only want to export what is currently being viewed, make sure that check box is checked, then use the multiple file option (html and jpgs). Decide on a number of levels to export (each level will be approximately twice the size as the level above it), set a number of files horizontally and vertically, then set a resolution (say 516 or so) with no or very low overlap. Set your directory for export, then let FTPro do its thing. This will give you a number of images that you could stitch together to create a larger version with somewhat less pixelizing.
Perhaps Waldonrate (author of the FTPro software) will be along at some point, and he might know of a better way to achieve what your looking for.