Hey djordje!
Thank you so much for that trick with the StrongBox, I’m pretty sure I never would have found that out.
Writing some extra lines of code to get maxdist would have been my next approach, but then I was kind of interested in how to make this work.
Still it is kind of obscure to me, why the out values “plane” and “deviation” need to have their type already predefined, while the return value “planeFitResult” is dynamically set to the Rhino type PlaneFitResult.
Or how I could deduct from the documentation, that it returns a tuple, when I only pass the point list. I’m glad I don’t have to make this stuff up 
Thanks again for the example, this will also help in the future, when I run into a similar method.