Cliff ... Too much! Why not drop back to a 30-foot head that that weighs about 180 to 190 grains? It really doesn't matter whether you go with a sinker or a floater. But if is to be a sinker, I would recommend an intermediate because of the 5-weight rig ... That's about as light as I would recommend for a shooter in the 5/6-weight class. The lighter you go, the more tricky they can become.
Until you are comfortable with shooters, I would also recommend buying anyone's DT line to save money and minimize the effect of problems. For example for $14.40 you can pick up a Canadian made line from dorbeR. http://www.dorber.com/FlyLine.htm
. I consider these lines to be on parity with Corland's 333. As a learning line, the price it hard to beat.
If you go with a full sinker, stay with the 6-weight DT but when you begin head preparation, you may have to cut the head back bit more than the intermediate. If you elect to go this route, I will help you step-by-step as to what I would do.
On overhang: depending on the weight I'm throwing and the precise parts of the rig, I usually throw with a overhang between 1 and 2-feet. The leader in the case of either sinker need not be more than 3-feet. For the leader butt, I would experiment between .021 and .023 using plain old mono such as Stren. If you decide to go with a floater, I would pickup a furled 68-inch leader from dorbeR because of their inherent positive turnover. That alone might take care of the curve because "magic casts" are very sensitive to the leader's characteristics -- furled leaders do not do that job well.
Don't overpower the casting stroke ... with your upper body strength it can be the kiss of death. Try to think of yourself as 5.5-feet in height with a weight 105-pounds. Release the cast high ... if by chance the head wavers in the air, the overhang is too long.
Finally, remember that a shooter can only be shot or released to the rear on the final backcast; otherwise it will shatter.
Hope this helps,