I have been on many roofs, installing sheathing boards and then asphalt (bitumen) shingles over that, but have never worked with steel panels. I don't know how hot it gets in your area of Finland, but leaning on shingles all day during the summer here becomes a nightmare (a 32 C day on the ground can easily reach nearly 50 C on the roof after the tar paper and shingles are on!) Those sore muscles surely feel good, though, as they came from doing good work :) I am very pleased to know that you're writing an interactive story; I always loved reading the "choose your own adventure" books when I was younger. I have been writing a series of semi-connected short stories that take place in my own imagined version of Iron Age Northern Europe and Scandinavia; I have titled the collection as "North Lands"