Re: how to set chapter font bigger?

[Karl Berry]

    If the answer is only inside the texinfo.tex file, anybody knows more
    exactly where?

You guessed it.  Inside texinfo.tex, around line 2052, there's this
set of definitions:

    % Chapter (and unnumbered) fonts (17.28pt).
    \def\chapnominalsize{17pt}
    \setfont\chaprm\rmbshape{12}{\magstep2}{OT1}
    \setfont\chapit\itbshape{10}{\magstep3}{OT1IT}
    ...
    \font\chapsy=cmsy10 scaled \magstep3
    \def\chapecsize{1728}

I suppose you can increase all the \magstep values to whatever you like.

(This is assuming the default 11pt text size.  There's a second sequence
of definitions for the 10pt case, a few hundred lines below.)

Hope this helps,
karl