*Goes to jet onto ledge half the jump height of his spider and...*
Yeah, nothing. I hit a vertical wall that starts at the bottom of the structure and goes completely straight despite having fairly DEEP ledges into it's side that I could VERY VERY reasonably fit an army of spiders in.
Also, it's not just vertical. See this image below? I can't move forward. Yeah, that's where the hitbox for that structure is. 2 whole ~medium-heavy mech widths out from the wall. And it is actually very accessible to most mechs.

PGI. QUALITY CHECK. please. PLEASE quality check your maps. I mean, I can understand the vertical hitboxes on very not straight walls.. because the Spider with 2 CT energy and 12 jj's should never have a purpose other than being flying target, but at the very least, don't let there be a hitbox 2 mech widths away from the visual edge. You can park an atlas in full view and not be shot because of this hitbox.