OMG, this is devastating o_O. Three disadvantages:
1. When you will be mining like for few months/years, PCIE slots will loosen and get damaged (because the cards are not properly inserted into the slots, they're bent). You will have to buy new motherboard then.
2. The slots will loosen even faster, if you make the case stand vertically. You have to put this horizontally to work.
3. When you start mining, this setup will overheat with 99,9% probability. This is not for serious solutions.
No, it does not overheat. GPU temps are between 65 and 85C. Throttling doesn't happen until ~100C. Shortly after posting this picture I slightly changed my setup by putting the spacers near the end of the card where the fans are, for more efficient cooling, and slightly less pressure on the PCIe slots. This machine has been mining for 2+ months 24/7.