I have a letter which, visually and practically, will look nicer if all content, including the closing section (closing sentence + small image of a signature + name), is kept in page 1. The content, as seen in the following screenshots, is not much.
The letter is based on the following files:
(which are based on the files at invoice_el/tree/master/sources)
Update
As per one of the comments, the settings for the geometry package are overwritten by the KOMA option DIV=last. Even if so, perhaps the design of the page without the geometry options might be "ok" (as can be seen with \usepackage[showframe]{geometry}. To practically address the problem, the question can be: how can only the vertical size of the letter page be increased, so the closing and signature and name appear on page one?
Screenshots
Here is page 1

and here is page 2

Perhaps it is the (non-visible) footer that makes things hard to keep in one page? I have tried a couple of things to work this around (including suggestions from https://tex.stackexchange.com/a/4472/8272) without success.
How can I force the closing section to stay in page 1 like in the following smudged one page sample?

\enlargethispage{\baselineskip}or even\enlargethispage*{\baselineskip}(which tries to squeeze the text on the page together) before\close{…}? You could try different sizes instead of the\baselineskip. – Andreas Sep 20 '17 at 16:53\enlargethispage{..}as suggested by Andreas is normally the way to go. Or reduce the spacing in the text. – Ulrike Fischer Sep 20 '17 at 17:32geometryis loaded but later onDIV=lastis used. So every settings by\geometrywill be overwritten. – esdd Sep 20 '17 at 19:00\KOMAoptions{usegeometry}before loadinggeometry. Then replace your\geometrysettings by\geometry{verbose,bmargin=1.5cm,includefoot}and remove the laterDIV=lastin the argument of\KOMAoptions(in custom_invoice_template_el.tex). And maybe you want to change\@addtoplength[-]{firstfootvpos}{\useplength{toaddrvpos}}to\@addtoplength[-1.2]{firstfootvpos}{\useplength{toaddrvpos}}%in the lco file. – esdd Sep 20 '17 at 19:10\enlargethispage{..}too, does not work as expected. @esdd Thanks for pointing to errors and suggestions. I will test and try to improve. – Nikos Alexandris Sep 20 '17 at 21:41usegeometryto the class options (and remove\KOMAoptions{usegeometry}from custom_invoice_template_el.tex. – esdd Sep 21 '17 at 09:15\@addtoplength[-]{firstfootvpos}{\useplength{toaddrvpos}}altogether. – Nikos Alexandris Sep 21 '17 at 21:45