I'm pretty sure the SL8s don't have threads, if you REALLY wanted to put a flashider/suppressor you could buy a G36E barrel extension (I'm pretty sure the SL8 barrel/inner barrel is longer, so it’s your call on that). Personally I would just leave that as it is, SL8s don't look good with flashiders anyway, IMO.
And no, you can't fit a battery in the stock...
Some good upgrades for it are new contacts and a G&P m160 motor. Together they will greatly raise your ROF and speed up your trigger response time. These along with a new barrel, bucking, and h-nub will pretty much optimize your rifle’s performance- but don’t forget a 9.6v battery if you don’t already have one.
