Congrats on Chilly and Gizmo!
I love Robos! They are amazing little creatures! I agree, two wheels are a great idea! Mine usually use one together, but occasionally they each use one...this will reduce the chance for fighting. Also, use caution when handling them...they are really fast and can jump!
I have mine in storage bin cage I made myself. It's filled with a ton of toys and things for them to chew on.
I would say to just keep an eye on them for fighting. I recently had to split 2 of my girls because one had bitten her sister and she is missing hair from her buttock area! She is fine, just needed some antibiotic ointment, but keep a close eye on them because you never know! I have 4 female robos, 2 robos in one cage and now 2 separate cages since the fight.
Good luck!