I'll have to look up Trapunto and see how it's done. I may try my 12oz weight batting for the next one and do tight stippling all around instead of the outline. I think part of the problem is the weight of the gold fabric. The lightweight muslin on the back is plenty puffy!
I prewash all my fabric (including backing, but I don't prewash the batting) so I'm tempted to wash the block to see if it would puff up more. I normally wash my quilts after they are quilted and bound, and they seem to puff up quite a bit more after being washed. But I'm a bit leary that it might change enough in shape to make it difficult to put together with the rest.