EBlack36, what type strut rod eliminators are you using? Did you weld in any additional supports when the eliminators were installed?
As far as weight goes, Ford's not the first to use that type suspension. If you've ever seen a 64 or later Rambler or AMC, you'll see the same thing. AMC started using a strut rod (compressed, as with the MII) in 1962. The lower arm with ball joint and crossmember is very similar to the MII unit. The only significant difference is the location of the spring -- it's above the steering knuckle on the AMC design, similar to an early Mustang/Falcon. AMC used a big, heavy 287 and 327 V-8 at the time, about the size and weight of a 396 Chevy or 352/390 Ford engine. Only spring location is different in the small Fords too -- Falcon and Mustang used a similar setup. I think the Fairlane did too, but had front strut rods (in tension) rather than rear (in compression). So the overall design isn't flawed -- it's been used for years in different variations.