Rever,

While the lines weigh the same in the first 30 feet, naturally the weight forward line will have more weight distributed closer to the end than a double taper line. The double taper is great for a fine presentation while the weight forward helps punch the line when using heavy flies or fighting a wind, etc.

But, I suspect your problem of the line messing up on the back cast is not a problem with the line (if it was it would mess up on the forward cast as well) but rather your casting technique. Pay close attention to your back cast and you should see where the problem is. Timing is everything in casting. We sometimes tend to do a 'proper timing' cast on our forward cast because we can see it, but on our back casts, we will either hurry it up before it loads the rod properly or wait too long so the rod starts to unload on its own.

Go out and catch some fish.

Larry ---sagefisher---