The light is the same size as my G&P M4A1. 10.5" barrel, more than enough for out door play and great for crashing through bush. I don't try to push it much past 150ft when I'm in the clear shooting at people.
That being said, I bought my G&P for $350 used with upgraded internals. So...$6 more than the G&G and a much better gun.
The blow back model. Avoid.
Blow back = greater chance for something to break. Most people who've had a blow back gun disable the blow back feature.
As for the "size" of the gun. The stock is adjustable, it'll fit almost any body type/size.