WOW!!! Congratulations Calum, quite an enjoyable model to put together for sure.
I put in a 5 valve block & it seemed to spread nearly the entire width... 6 will be tight!
I also use a 3s 5000mAh lipo from Team Enrich-Power that measures 135mm x 42mm x 28mm
The hyd pump that comes with this model is ridiculously fast & with such small bore cyls, cycle time is very quick! even with the motor rpm at 50%. I set my pressure to 18bar, seems plenty to keep the model planted while digging.
Good luck with the build, hope it goes together easily for you.