"Watch and Try" - desiging a course to be viewed side by side with a test environment

Wonderful E-Learning Heroes community! I'm working through an idea and wanted to get perspectives from the experts that provide me so much insight here in the community.

I have a process training course to create where I want the learners to watch a segment on how to do something and then try it themselves in their test system environment. It's impractical to create a simulation (and of greater value for them to use their real environment) and my current plan is to have them run the Storyline course in a window side by side with their test environment to easily watch and try. Here are my questions:

1. The screen sizes will vary, though I can safely assume they'll all be "wide screen" and can accommodate two simultaneous windows - any recommendations for the story size?
2. Should I attempt to start the course at a standard size ("full screen") and switch to the side by side view after instructing them to arrange their windows? If so, I don't believe there's any way to change story size mid-session, so could I "shrink" the used area without creating confusion for the learner (with unnecessary scroll bars and such)
3. Has anyone done something like this before and can offer some suggestions or possible challenges I haven't considered in using this method?

I look forward to any feedback you care to provide!