i too just recieved my TM MP5 SD6 a week ago. Although it is my first AEG i am pretty impressed! I slapped in a Systema 6.04 M4A1 tightbore a couple days ago and trimmed it back to fit about 1/2" from the front of the silencer and it works great! I love the SD6 because of the sliding stock! I've never really liked the full stock variants.
BIGGER is BETTER