The TT GF4 cooler is a waste, it doesnt not cool much better then the stock one. i would recommend putting in some more hours at work, and getting the turbo model, this way you wont have to worry about a new heatsinks for it, cause the stock one is awesome
I don't think your need to go spend money on a TT Geforce 4 cooler. Although the penny is mostly copper, I doubt it is going to tranfer heat idealy well, even if it does, it does not have much surface area. My sugestion, is to keep the stock HSF on the core, and for the back use an old P1 or older ATI HSF on top of the penny. This will save you money, and you will probably get the same proformance. Don't forget to use artic alumina adhesive, and to lap the penny.
Also, I'm not sure if the penny would short out the card. I'm pretty sure it won't, but I would wait till you find out for sure before going all out.