Will it be a four-bar lifter like Biohazard or fork lifter like Panic Attack?
Doesn't the Spektrum DX5E have built-in mixing?
How will you control the lifter? Another BotBitz 85A ESC or using an H-Bridge?

I know it's just a mock-up buy, when you get the actuator, make the robot as compact as possible, you will save lots of weight and money in materials.

Looking good.