Why are we at a gametable? Why are we playing this game? To Win. Not many players show up to a game and hope to lose. It would be nice to win. It would be nice to win the turnament. [Exception: Testing a new list or using a real cool looking Lame model, not planning to win just test or play the model, even though it sucks.]
Currently we are being lawyers (good type) on this Case or debate. ( there are good and bad types of "Game Rule Lawyers.")
I and others got out the books and re-read the rules. That is what lawyers do. We can Give away a game, by aiming that flamer at a corner of the vehicle, covering no troops behind (As if your opponent placed the template. )
That is playing to the letter of the law. It is not needed. We should "Try" to cover most of the vehicle and get as many of the troops behind it as we can.
We are here to "not lose". I think it is OK to target Some of the troops behind the Vehicle. As long as the flamer covers a large part of the vehicle.
I can see shooting (or being shot at) in the diagram by SaintHazard.

Researching rules AND Rule lawyers. How should be play the game, should be expanded to forum debates of their own.
Getting into a game[ not intending to lose.] We are going to have "cover save" and Template placement issues on how exactly the templace should be. I think if the opponent agrees to the placement of the templace, that is OK. The opponent could say the rule " You have to cover most of the original target first"