91TwighlightGT
Dirt-Old 20+Year Member
A couple of companies out there (Kenny Brown, Maximum Motorsports, etc) still make bolt on rear strut tower braces for the Fox bodies. They're not a cure all, but they'll help to some degree. More so on a hatch back than a coupe. A roll cage pretty much solves all of your flex issues.
Three attachment points are better than no attachment points. While I agree that a hatch isn't going to stop the flex, it will reduce it to some degree. Ever grab an old suit case, or lunch box by opposite corners and twist back and forth while it was open? Now close the lid (that's held on with two hinges and a latch, much like the Mustang) and give it a try. Not quite as easy is it.
For however flimsy the car remains with the steel hatch, it will be even more so with the fiberglass one on there. At least the steel hatch itself holds a more rigid shape. Add a fiberglass...or even worse yet, a fiberglass hatch with a lexan window and you might as well just be running none at all.
Besides....when reducing weight, the last play I'd want to take it off is over the back wheels of a car that's already got a reputation for getting "squirrely" when the power is on.
The problem with that analogy is that the top half of that lunchbox is adding an equal amount of it's own torsional rigidity to your overall ability to twist said item. The hatch on the Mustang would be the equivalent of bolting a piece of cardboard in place of the lunchbox lid and then expecting it to have some significant impact on your ability to twist the box.
I suppose I can conceded that the hatch will offer some sort of resistance, but the effect is so negligible that it is in all practical purposes non-existent. But, we will just have to agree to disagree on this effect because neither of us can produce any numbers to prove it one way or the other.
The weight savings aren't in so bad a spot as you think. The weight of the hatch is quite high up on the car which is bad from a handling perspective. Given the percentage change in front to rear bias from the slightly less than 20 lbs you save from going to fiberglass from steel, I think it is still a net gain. Plus, as I've always said, you can always add ballast down low if you want more weight on the rear. Of course, no one adds weight unless they are trying to meet a minimum weight rule.
One other thing. Fiberglass doesn't rust
