Really nice job, congratulation!
I'm planning to use transprent plexi in my next project too. 
Then I tell you: you can use 3mm perspex one, but I woudn't do again at the rear part, as the cable is thick it will make preasure on it while moving, so you should use 4mm one, and you'll have to cut the plastic rubber of the cable where it plugs so it will let you introduce it, and you don't need to change the buttons. I've thought you can use the ones it has and use an small clear tube (or heat shink tube if you find black rods) to join them to the rods
