No, unfortunately it is not possible.
The length is 5.5".
The A2 Flash Hider will need to be removed to install the Guntec USA AR-15 Reverse Thread Slip Over Fake Suppressor.
The Guntec USA AR-15 Reverse Thread Slip Over Fake Suppressor slides over the barrel and can not be pinned and welded.
The Guntec USA AR-15 Reverse Thread Slip Over Fake Suppressor has an outside diameter of 1.25". The DDM4V7 MFR Rail has an internal diameter of 1.39", so the Guntec USA AR-15 Reverse Thread Slip Over Fake Suppressor will fit in that rail.
The Guntec USA AR-15 Reverse Thread Slip Over Fake Suppressor has an outside diameter of 1.25". So it should fit fine under your Diamondback Handguard, however since Diamondback Firearms does not state the internal diameter of their handguards I recommend contacting them to confirm.
The Century Arms Draco NAK 9 has a muzzle threaded for 1/2x28 RH threads. The Guntec USA AR-15 Reverse Thread Slip Over Fake Suppressor 9mm model is compatible with barrels with a 1/2x36 thread. So it will not work with the Draco NAK 9.
The Guntec USA AR-15 Reverse Thread Slip Over Fake Suppressor for .223/5.56 will work with barrels threaded for 1/2x28.
The Guntec USA AR-15 Reverse Thread Slip Over Fake Suppressor will cover 5" of your barrel once fully threaded on. So as long as you have 5" or more of unobstructed barrel space it will fit.
The .223 model of the Guntec USA AR-15 Reverse Thread Slip Over Fake Suppressor can be used with 5.56 and .223.