OP, you might want to give the bowls a little wash in warm water with mild shampoo or something - the brand new foam softens up a bit after the first wash, and over the period of a few weeks, will become even softer (Well, relatively. Don't ever think you'll approach XB500 territory)
Second thing you want to do is adjust the headband properly, so that clamping force is minimal. you do this by gently stretching out the metal loop under the el-cheapo vinyl covering - a J$ band in camel or brown looks really awesome on the 325, and is more comfortable than the stock - think about that too.
If this is your first Grado, give yourself and your ears some time to adjust.
If you still feel the bowls are too much, then Jumbos might be your only option left.
I wouldn't even be all that gentle with the headband bending; you want the headband to exert just enough force to keep them from falling off, no more. Also, bowls are more comfortable (don't pin your ears back as much, more of the pressure distributed to your face rather than your ears) and sound better (less upper-mid emphasis, better imaging) worn pretty far forward, so that the back edges of your ears are left uncovered.