The Sizer version that you would need to download and use is Sizer v4.0. The older version will not work with current versions of Windows. At first launch of a program window Sizer cannot affect the size of the window in any way: that first-launch window size is determined by Windows and whatever program you launched.
Your OpenOffice is working exactly as it is intended to: the size of the window on a new launch of the Calc should be the same size as the window size you last used with Calc — and it sounds like that is what is happening, so nothing strange going on there. In the usage scenario that you describe there is nothing you can do to make your windows operate in the way you would prefer.
What Sizer can do is allow you to very quickly re-size the currently
active window to your preferred dimensions with a mouse click or a hotkey combination. What to do is 'install' Sizer 4.0 (as a portable) program in a folder called "Sizer" exactly as I described in the other thread. Once that is done precisely as described shutdown Sizer then do the following:
(1) In the Sizer folder rename the file
sizer.xml to
sizer_original.xml. In this way after your initial experiments you can get back to the original configuration if you so please.
(2) I have attached here a copy of my own configuration .xml file for Sizer. Place that file in the Sizer folder you created.
(3) Now launch Sizer. When it loads it will use that configuration file for the values of how to size a variety of windows to pre-set values.
(4) In that configuration file I have placed a pre-defined size for your 'Risk' spreadsheet. The width of the window will be one-quarter the width of your monitor in pixels (which is what you say you want). The height of the window is set to be 1169 pixels — this is suit my own monitor resolution of width 1920 x height 1200 pixels and is minus the pixel height of the Windows Taskbar. You may need to adjust these values to suit your own monitor resolution. However, if you study some of my other entries in the configuration .xml file you will see how to define size values precisely according to your monitor resolution.
(5) Note if you choose to make hotkey combinations to invoke a particular window size for the
active window you will need to check that the hotkeys you assign do not conflict with other hotkeys that your system or active program is using. Strange things might happen if there is a conflict.
(6) Now that you have Sizer running launch your 'Risk Spreadsheet' and, once it is launched and the Calc window is
active press the key combination Ctrl+Windows+Z and choose the 'RISK Window' option that Sizer presents — your Calc window will be positioned to the left of your screen and at one-quarter width of the screen.
It does take a bit of figuring how to use Sizer and define coordinates in the first instance but once that is done it is a highly useful program to have on the system. I use its functionality every day.
If you do get round to experimenting with defining your own size values do remember to click the 'Apply' button so that you new settings get enforced.