Also, make sure that the character rig has a dummy named "FIRESPOT". This is what GG will use to attach and align the VWEAP model to. If no FIRESPOT is present, the weapon will probably end up protruding from the character's crotch or something awkward.
Gigabyte P67A-UD4-B3, Intel Core i7 2600K (passmark 8555), 16GB Corsair DDR3, EVGA GTX 970 SC (passmark 8637), Win10 Pro 64-bit, Primary monitor @ 1920x1080, secondary monitor @ 1280x1024