The Viper's have been great cars in both FM3 and 4. They unfortunately earned the moniker of LB car in FM3, as they dominated the S class leaderboard, so it was frowned upon if you pulled one out in a public lobby. I think that rep may have carried over into FM4. I've always liked them myself. They have a ton of natural downforce and generate alot of grip. They're a blast to drive and as stated above, are an excellent car for those who are not as skilled with the "twitchier" cars. That growl from the engine is just beastly as well!!
In the real world, weight reduction is everything, hence every racing series strict specs on weight. As we all know, the game doesn't always follow real world physics. The key is balance. As long as you have sufficient power to move the weight, the car will be competitive. Overpowering a light car will make it very difficult to drive most of the time. Two key stats in the game I have found are acceleration and grip. A power build may work on speed tracks like Laguna or Road America, but in the hands of a skilled driver a handling build will trump a power build on a more technical track every time.
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