one of the reasons newer iphones "feel like a brick" is that they transitioned to heavier materials (stainless steel instead of aluminum) and because the corners are now squared. rounding corners often has the effect of making things seem thinner as well as usually making things more pleasant to hold. I agree with you that these users probably don't want a thicker iphone, but I would bet if you focused on perceived bulkiness in the industrial design, you could sneek in a slightly larger battery and still give the impression of a less bulky device.