The weak points with regards a UAV design, are in rough order - airframe limitations (quite easy to design an airframe - with modern composites, to withstand 20 - 30g. You only have to look at the range of design techniques in R/C model aeroplanes to composite manned aerobatic aircraft to see the g tolerances which can be engineered into a design) The fuel system, engine and finally avionics, which being solid state can withstand serious amounts of g in flight. 8g is a relatively low load for an unmanned aircraft; you have already removed the biggest limiting factor - a person. The avionics g limit is less of a factor than fuel system, g will starve an engine of fuel if the system is not properly designed, that is with either piston or jet engines.
In reality the flight envelope the UAV operates in, is unlikely during normal flight, to ever get towards G limits, why would you want a 20g turn as part of the normal flight profile? The worst loading would be during the recovery stage which is sometimes into a net – causing serious deceleration loads, 100kts to 0 in as little as 10 feet.
Large UAV’s such as Reaper operate a conventional flight profile – with a wheeled takeoff and landing, rather than some of the smaller UAV’s which are catapult launched and net recovered.
G stress loading is a consideration, however bigger considerations to the designer are speed, endurance and stability. UAV’s tend to rely on aerodynamic stability rather than FBW electronic stability (lower power consumption for the avionics, with the autopilot not having to constantly compensate instability, giving greater reserves / weight savings on internal batteries)