Theses, Books, Title pages ⇒ The Legrand Orange Book template, b5 spacing issues

[Rasmus_Lind]

I'm trying out "The Legrand Orange Book" template for a book project. When changing from default a4 to b5 paper size, I run into some spacing issues. Specifically, I wonder if someone familiar with the template knows how to control the vertical spacing between the chapter heading image and the start of the chapter sections/text?
The "quick fix"
\geometry{
%top=3cm, % Top margin
top=1.5cm, % Top margin
}
works for the first page in each chapter but then messes up all other pages that don't have the initial image on top.
Thankful for any advice.