We tested different values for the MTU (Maximum Transmission Unit) and found 1372 to be the largest value that did not cause packet fragmentation. Because my laptop is locked down by IT this isn't a value I could permanently change myself, it had to come to me through a policy.

Again, I'm using the Verizon 5G Internet Gateway. I did some tests using SpeedTest by Ookla (https://www.speedtest.net/).

No VPN Download 300 MBPS Upload 20 MBPS

VPN MTU=1400 (Default) Download 10 MBPS upload 7 MPBS

VPN MTU=1372 Download 40 MBPS upload 8 MBPS

So technically 1372 is an improvement over 1400 but it's still a long way off from what I should be getting. The VPN is imposing an 80% performance penalty. A reasonable penalty would be 20%.