Best practices for logo sizing (in theme?)

Hi all-
We have a company logo, which I'd like to keep in the header/theme.
For this survey, we have an additional program logo that will likely be larger than the company logo, located above the first question.
I gave up on putting the program logo as a graphic item within the survey itself, it wastes a lot of screen space being placed below the theme logo. When I try to create a combo image to replace the theme logo, I can't figure out how to optimize the sizing.
Currently I'm just placing both images in powerpoint and saving as a combined image, based on the relative size of the two images and how far apart they might be if the logo was maximized for the width on mobile (the same size could be used for the browser version as well)
So basically, I'm trying to accomplish the first picture, but ending up with the second.
I welcome any suggestions on how to maximize the logo width for mobile (whether that is a setting, a change in the original picture size, or anything else!)