It's not going to fit unfortunately, there's 4mm of space between the GPU PCIe and the Spine. You'll need 7mm to fit a 2.5 drive :/
I'll help you with this a bit closer to the shipping date friend 
Sounds like a cool idea though!
This is a nice idea! However, there are 3 issues; noise, efficiency and cost. I'd still be super interested in seeing somebody mod the original design this way
Noise
- 2x80mm fans vs 1x120mm fan will produce a high frequency sounds that will more audible compared to the larger fan.
Efficiency
- 2x80mm fans vs 1x120mm fan will have lower airflow compared to the larger fan. Also, as [USER=6179]@For_Science[/USER] demonstrated a while back, having the fans to close to a solid surface will drop airflow pretty dramatically. There is not much room to move them back/forth either :/
Cost
- The CNC techniques here are a bit more complicated (also more parts involved), so we're probably going to land on $99 rather than $59.
Update #1 on the Kickstarter campaign shows a couple more pics of the different colors. In short, these are our color targets:
- Steel - Macbook pro Silver
- Dark - Macbook pro Space Gray
- Stealth - Razer Core Black
