I couldn’t stand the feel of the Lego back, after about a week of perseverance I gave up and had to change backs.
I ended up missing the lightkey, I could play many PSX games or SNES games without changing button maps. So I ended up fixing the lightkey to the flat back with a bit of thick craft mounting tape from a craft/hobby store. Thought I’d post here to show anyone who has the same issue as me.
The cable routes nicely behind the battery module and through the gap in the top behind the main board module, with only a little sticking out above the lightkey. Gameshell feels so much better to hold now though!