I think railguns should do +1 damage
To put it simply, when a structure breaks two weaker structures, it doubles the speed. This is called a Railgun!
There's a lot more depth here and some cool ways you can use this, but it's fairly difficult to line two structures up perfectly and actually hit someone with it at higher paces
I think additional damage would be fair (and make sense) since the structure is moving way faster then normal (that's gonna hurt)
it would also make it feel like a mechanic which i would like
I don't think this would negatively impact gameplay as railguns are already quite rare and very easy to shut down.
It would just give more of a reason to use them in combat and make them feel more rewarding to land in my opinion