Welcome to humblepieville...population you (and nearly everyone on this board at some point when they first picked up their M5/6
).
Now having tasted the homecooked pastry made by someone else, let me offer a few suggestions and see if it might help.
1. On dry street pavement I love the so-called "crippled" US launch control. In my opinion it is not crippled at all, just limited. You must, I repeat *must* push the gas pedal past the halfway point, yet not to the floor. I usually choose 3/4's down to the floor. Once you let the SMG center console gearshift go, you will take off like a bat out of hell and you will need to modulate throttle. I highly suggest practicing several times and then using it every once in a while so you don't forget how to work the pedal. Here is proof of what our cars can do from a standstill. I don't care who meets me at the line with more torque, there's a strong chance they're going down if they line up against me in my M5.
2. At the drag strip do not try US launch control, it will be worthless. Rather, use the mash and go technique. This will do a drop-clutch launch at 4,000+ RPMs and you'll need to immediately modulate throttle. You could also do this on the street, but it may induce too much wheel spin too soon and there is a slight delay as the ECU revs the engine and drops the clutch. I much prefer option 1 listed above on the street when you have the prep time (otherwise, mash-n-go is all you have).
Bottom line, you just need some practice to launch the car well and hit your shifts perfectly. The E55 has more chance for wheel spin than you do so hang in there.
Regards,
Darren