I have tried to replicate your problem on my own computer but can't.
This is the setup I tried.
Laptop with Hoster control panel showing for DJ, from the VGA out I connected a VGA to video converter (as shown in attachment "VGA conv,") . This has outputs for VGA, svideo and composite video. I connected a VGA monitor to the VGA out and an svideo out from svideo out socket at the same time. I had pictures on both external monitors with no loss of picture area.
But my resolution from the Windows/display/screen resolution was set to 1366 x 768 this is shown as the recommended in the windows setting as you can see in the attachment "Screen resolution".
With this VGA to video converter you do not need a splitter cable. If you are interested in this converter there is one for sale on Ebay at this address:
http://cgi.ebay.co.uk/PC-VGA-TV-Vide...item563b59151e
Also on my system, if I show a video it doesn't stretch it to make it out of proportion, if the original video is 4.3 that is how it displays it.
I haven't seen any mention in these posts as to what version of Hoster you are running my above tests were done with 4.21.
Hope this helps you.
Roy.
Roy