In reality I'm not sure if the cowlings would be completely detached from the airframe for maintenance but, if you had some sort of small diorama in mind, might you not paint them and then show them beneath the Mossie as if the maintenance mechanics had put them there? Sorry if this is a stupid suggestion - just trying to provide an idea to use those parts.
Your build is fascinating and I'm im awe of the detail in the kit and how you've managed to bring it all together so far.
You're doing a great job!!