I can't speak for fiberglass bows, but I can tell you how see your question as far as self bows go. Many people make their self bows with either a stiffer or shorter bottom limbs for a Mediteranian release ( one finger on top, two underneath ). Many people also go for a completely even tiller with the same release. I'm in this camp. But if I arrive at the weight I want with one limb just slightly stiffer, I'll go with it and make the stiffer limb the bottom limb if the bow design allows for it.
However, if I shot three fingers under, I would definately try to keep the bottom limb stiffer. Just because that kind of release puts more tension on the bottom than the top. I think it is more critical for this kind of release as opposed to one finger on top and two under. Just my opinion.