Do I really need to use the first PCI-E Slot?

Hey everybody, I just got my corsair 460x case and I'm finishing my build but my MSI GTX 1070 Aero card does not fit in the PCI-E-1 slot as comfortably as it would in the PCI-E-2 slot. On my motherboard manual it says to use the PCI-E slot for optimum performance. I really want to stick it in the second slot for optimal aesthetics, does anybody know if there is actually any downside to having my single GPU in the PCI-E 2 slot? Thanks for any help guys.

Here's what I'm working with:

MSI PC MATE B250 Motherboard
MSI GTX 1070 AERO GPU
CORSAIR 460X RGB CHASSIS
CORSAIR H80i v2 CPU Cooler

From the manual for your motherboard, the speeds of the PCIe slots. The second slot is considerably slower.

if that slot was an 8x slot then it would be fine, however at 4x you will get bottlenecked

Its suggested to use fastest slot on your board in your case the largest one. If you put it anywhere else card might not be used properly by machine

you should use pci-e 2 it's 3.0x16.
the others are below x8 and will bottleneck your card.

you should use pci-e 2 it's 3.0x16.
the others are below x8 and will bottleneck your card.