Automotive Ethernet and GVIF2 Passthrough PCB Design Discussion

[Unsanity]

Hello,

I am designing a passthrough PCB for Automotive Ethernet and GVIF2 communication lines. The reason why is because the wire-to-wire connectors are not available right now. So, I am making a PCB to connect two harnesses together. The wires of the harness are STP (Shielded Twist Pair), and I would like to continue the continuity of the shield between the harnesses. I assume the cable has an impedance of 100 ohm, but I do not have any specification to back that up.

Each wire has its own shield. I decided to keep each shield plane separate to help prevent noise from traveling between shields. I have stitched the top and bottom layers together to create a cage around the signal traces. No idea if this will actually help, just felt good to do.

If there are general comments, please feel free to share too. I am far from an expert 
Sorry if I missed to add any important information needed for an informed discussion.

Question
Is it OK to stitch the top and bottom layer shields together?

Layer Info
Layer 1: Shield
Layer 2: Signal
Layer 3: -
Layer 4: Shield

Stackup Info
See attached images
Inner Copper: 0.5oz
Outer Copper: 1oz
Prepreg Type: 7628
Prepreg Dielectric Constant: 4.4

Differential Pair Design Info
See attached images
ZDiff: 100 ohm (Ethernet and LVDS)

[nctnico]

I'd crimp RJ45s on the cable and used a shielded RJ45 to RJ45 coupler.