about the video, you hold the carbine wrongly, first of all the front grip is for a purpose..... USE IT!, if you would fire a fully atomatic burst you would feel a thing in your arm (or your shoulder for a week, trust my i've been there) any ways on topic, this MA5K is awesome, i wish that i could sculpt that wellor build or anyhow u build it
(and belive me i talk with a voice of experience about the front handle and, after 4 years with the french foriegn legion it is not wise to hold a carbine this way, and the mag is undersized in odst it can hold 32. 7, 62x 68mm rounds, it couln't even hold 15 if my math is correct)
and the carbine is undersized, it should be around 10% longer, but your height is correct.