I added a yard of lead tape to one of my racquets and will give it a try. I think that I've had this amount of lead tape in the past or maybe more but I took it all off at one point. I think that was during a period when I strung the racquet at lower tensions than I do know.
At any rate I'll try to get some serves in tonight to see how it feels. From memory, it should make quite a difference.
I weighed the racquet today and was surprised to find that it only weighs a pound. This was with a high-quality electronic scale at the office. I though that it weighed 17 ounces but that must have been when I had all of the lead tape on the head.
The racquet definitely feels heavier at the moment though I'm limited in my swinging it around at the office.