Not a direct answer to your question, but this will answer part of it. 
Gouwa stated the room reserved for heatsink in this post.
Area reserved for heatsink:
25 x 32 x 5mm
Looking at the picture in Gouwa’s post, the heatsink appears to be a 25x25x5mm( I assume 5mm) heatsink. It is approximately 11 GPIO pins wide, turns out that is ~25mm.
