Vehicle mounted machine guns

[B.T.]

I am very uncertain, how to solve "Firing" tasks with Machine Guns attached to vehicles. There are two different things, that I'd like to have your opinion on:

1) Firing with a co-axial MG on MBTs and IFVs:
If I understand it correctly, the person, firing a co-ax, uses the same optic and firing system as he uses, when firing the main-armament. I therefore think , it should be used with the same skill. The weapon is different, but the gunner of a MBT just pulls another trigger/pushes another button He does not really lay his hands on the MG.
This is no problem, if you have a vehicle like a Marder or M2/M3 Bradley, because both weapons (co-ax and autocannon) use the same skill. But what happens if you are firing the onboard M240 (co-ax!) from the turret of a M1 Abrams?
BTW: Does the firing character on a Bradley fires the TOW with the same optic/fire-device, or does he really uses another device for aiming (Yes, I know that you can't fire the TOW, when the Bradley is on the move!)?

2) What about the recoil of vehicle mounted MGs? I know, that such a weapon can be attached in various ways, what means: You have to look at every single situation.
- If a MG is attached with a homemade "pintle mount", say on a truck, the usual prodedure is okay: The MG may fire normally with the recoil value with bipod.
- If the vehicle has some specialized mounting system (For example: M1025 weapon carrier), does the firer use the tripod recoil or does the mounting system competely negate the recoil?
- And what about the M2 .50 cal for the commander of a M1 or M113? How does the mounting system work? And what does this mean for the recoil: Neglect or tripod mounted?
- What about a M60 or M240, fired from the passanger roof shields on a M113 ACAV?

All other weapons use the info from the weapon chard: If a character fires a MG from the open roof hatch of a M113, he may use his bipod or fire it from the shoulder. The basic rules make tasks harder, depending on the movement.
A Character, who fires from a gun port, has no benefits regarding recoil, right?