Modeling Advantage

Blood Angel Razorback conversion

Depending on your playing group you may have heard accusations of 'modelling for an advantage' before.
For those that haven't or those that don't know the meaning of the phrase I'll briefly explain.
The term is generally used to describe conversions and usually for larger models like vehicles or monsterous creatures.

Its meaning is rather clear, it is the suggestion or accusation that you converted the model in such a way that improves its abilities in play when compared to the standard/official model (if there is one).

I've seen several examples of this over the years, this can even be simply things such as:
* Modelling Chapter Master Gabriel Seth on a 40mm (terminator) base rather than his usual 25mm (standard) base so that he causes more hits when he uses his Whirldwind of Gore ability that strikes all models in base contact (maximum of eight rather than six).
* Extending the barrels of weapons to extend the range, since vehicle weapon range is measured from the end of the barrel.

More complicated ideas are more common as the base change above isn't likely to even be considered a conversion. It would still be considered 'modelling for an advantage' however.
Take the pictured example above, this conversion was done by a friend of mine to give his Blood Angel Razorbacks an unique feel when he changed his list from Rhino's to Razorbacks (not to mention wishing to avoid losing the work he put into painting the rear hatch).
Yet going by the model some may claim he is modelling for an advantage. The reasoning?
Unlike the official razorback model, his one can easily have more than 50% hidden behind a building and thus gain a cover save while firing the weapon and only having its front armour visible. For a standard Razorback you'd either need cover of the right height to hide the vehicle or have your front behind the building and your rear sticking out because of the guns position. In addition he would gain a few extra inches of range over the standard model when shooting in front.

There can be many solutions to this problem, depending on the model and the players. Since my friend wasn't actually after an advantage and it is still a standard rhino is size, we simply measure line of sight and range as if the weapon was in the normal official models position. Similarly you can house rule that the above Gabriel Seth idea has a cap of six hits no matter his base size.

Sometimes things are not as easy, especially with heavily done conversions. Here GW has thrown a bit of a curveball with the new releases coming up, primarily the fierce looking Tervigon.

Quite a few Tyranid players have converted themselves a Tervigon since they are so impressive in play and most of the conversions I've seen have been remodelled Carnifex's, yet now an official model is coming out we see the real thing is much larger, both in that it uses the larger base (one used by Valkyries, Storm Raven's, Razorwing Jetfighters etc) and is taller. So while they obviously can't be accused of modelling to an advantage since there was no official model to compare their conversions to at the time, these Tyranid players still have an advantage due to the smaller model (hiding from line of sight, gaining cover etc).
Similarly it seems that Fenrisian Wolves use 40mm bases and may be larger than expected, which may bother a friend of mine who has been using fantasy wolf models on fantasy cavalry bases (I'll agree these are likely less used than Tervigons but the point is there).
There are some solutions, such as rebasing old Tervigon/Wolf conversions on the larger base with some base scenery that ups their height near that of the official model etc, but will that do the job enough to appease everyone?
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Do you think the average player would complain about the use of such old models now the official ones are out? What about tournament play where things like the Tervigon size may be highly important?
Personally I'd be hard pressed, as my main passion is for modelling and mild conversions I'd be reluctant to disallow something someone has worked hard for, yet unless they have redone and base etc I'd still feel somewhat cheated to have it in play since I'm also a bit of a stickler for rules...