[Ripplinger]

I think was referring to the width of ereader screens being around 3.5" (looking at my 5" Sony it looks about 3").

I don't have a 6" reader, just my 5", but I figure if the layout looks good on the 5", it should work on the 6" just as well. I never bother loading them onto my phone to check it breaks anything, it's just too tiny for me to even consider reading from and don't think the majority of people read from their phones.

Like theducks, I try to keep the layout of books I do as close to the original as possible, as long as it also looks good on the ereader, including any images in the original. I'll generally try to code the first few pages that have the title page, publishing info, dedication pages, etc., in fixed fonts and layouts, just to keep their formatting which usually looks best kept to one page for each. But when it comes to the main part of the book, I don't specify any font so readers are free to change it to whatever they want. While I can't test it on a 6" reader, I do test various fonts and sizes on my 5" to be sure nothing gets broken (or even bad-looking) when they do change.

About the only exception to this is that I'll add a TOC even if there originally was none in the book. I can't think of any reason why someone wouldn't want a TOC if possible.