Hey, that's actually a great question! First off, you might already know this, but just fyi: Being class A is very hard nowadays because most auditors assume (for whatever reason) that you're at least class B. But that's not super relevant here because you're looking at classes B and C anyway :)
Regarding your question how much harder it is to document class C software: When I started out as a consultant, I thought class C software would be pretty hard, but in reality that's not the case. My estimation would be that the main work would focus around:
- Documenting detailed design: This is essentially another "level" below your software requirements, so you'd have a hierarchy of User Needs --> Software Requirements --> Detailed Design. Of those, only Detailed Design is required for class C, whereas User Needs and Software Requirements are required for all classes (simplified).
Also, my experience has been that auditors tend to not check the actual content of technical documentation like the items mentioned above. That's because most auditors have no clue how to write code. So it's likely they'll just check whether you have detailed design and not whether it makes a whole lot of sense.
Like most other things, this just ends up being a documentation exercise. And the amount of work will greatly depend on how many software requirements you have, because you'd need to aim for at least one detailed design "item" per software requirement.
For what it's worth, we added class C support to our eQMS, Formwork, a while ago, so that would be a cool way to fulfill this requirement (yeah, this is an obvious plug for our software, but then again, I do believe it's the best way to document this sort of many-to-many related stuff). - Additional testing: The IEC 62304 has some additional testing requirements for class C software. I can't remember from the top of my head, but there might have been something like testing for memory usage and similar stuff. So, in your software tests, you'd need to check whether you're testing for those conditions, too.
That's it "already". I think it's doable in general. Somewhat surprisingly, after dealing with ~200 consulting clients, we still have never encountered class C software. I mean.. I'm sure it exists, but it's interesting to see that only a tiny minority of companies are building it.
Hope it helps and let me know if you have any further questions!
