You could do it that way, but that makes your grip size larger. Since the center of mass of the lead would be at 4" from the butt instead of 8" it would also make it more head light.
What I did was buy this: http://www.tennis-warehouse.com/descpage-LEAD.html
which is 1/2g per inch. 36 inches is 18g, so I cut it in half and had two 9g strips - each 18 inches long. I then unwrapped the grip about an inch and wrapped one strip on each of my racquets I was modifying. It wraps around about 4-5 times. I then used a rubber grip finisher on my Tours that I don't on my Diablos to get it to about 10g. By putting the lead at the top of the grip it is not under your hands so it does not enlarge the grip at all and it keeps the racquet from becoming too head light. My Diablos are only 8-9 HL with over grip. Yours may be more head light so you may want to have some of your weight below the top of the grip. You could do one or two wraps just above the butt cap instead of it all at the top.
I wouldn't take my numbers as the exact ones to match YOUR racquets. Take it as a really good ballpark. If you do about what I said and go hit you should be able to tell if you enjoy it enough to continue tinkering. If it feels almost right you can move the lead a bit, add a bit or remove a bit. Heck, you don't even have to put lead at the top of the grip to test it. You could put two nickels at the top of the grip - one on each of the big sides - and wrap electrical tape around it. That would add about 10g. Two nickels and a dime would be about 12g. You could hit with it for a while then try it with one nickel at the top of the grip and one taped to the butt cap which would make it more head light. Easy, cheap and it would let you know if it is worth pursuing tinkering before buying a Rebel. Coins aren't a long term solution but are quicker and easier than moving lead and re-wrapping your grip each time.