If I or any user comes up with some tip to ease usage I'll be adding it here.
Note this tip has been included in height's documentation.
This might not be obvious at first glance but you can set the width manually in a very simple way.</p>
Although capture width cannot be set directly it can in an easy enough way:
Let's say you want your captures from a 640×480 source to be 1024×300, using -H300 would lead to captures being 400×300, you would need to do some numbers to adjust the aspect ratio to match the desired 1024×300 (that would be -a3.41 or -a256/75)… but you don't need to set a canonical aspect ratio, just remember aspect ratio is the same as width / height and you can simply use:
-H 300 -a 1024/300.
Yep, not as straightforward as an hypothetical -W 1024 would have been but, oh well :P