The G mod is a good thing but don`t be fooled into thinking it`s an all gain,no pain kinda thing. First off when you relocate the holes the arms will hit the top of the perchs so you`ll need to do quite a bit of reshaping (without taking too much strength/rigidity out of them). The G mod helps out some with + caster but not as much as different arms can,the perch just doesn`t have enough meat to move the holes that far. The only way around these two problems is to cut the whole perch off,cut it down and remount it in a new more idealized location. It`s best to make a jig to ensure that they end up in the right place. I`ve done it a number of times and it`s a lot of work but it you do it right it looks factory. The other issue is that when you lower the holes it adds + camber. Lowering the car also ads + camber. Even with the G mod you won`t start getting any - gain until it`s pretty low and then it`ll be very mild (but at least it won`t be + gain!). BTW we can achieve even larger gains with just a tall upper ball joint. At any rate when you go to align it you may not be able to get the specs you`d really like to have even with big stacks of shims. Offset cross shafts may be necessary to get any kind of decent performance alignment out of it. It varies from car to car and with ride height but you should be aware of it. Dick Guldstrand`s cars had stock *appearing* upper arms on them but that doesn`t mean they *were* stock dimensions and shape.

I`ve modified a number of sets of arms myself and while they work fine and you`d never suspect by looking at them they all took a lot of time in design and fabricating work to get them just right.
I`m not trying to talk you out of it,just giving you a heads up on some of the technicalities. However you do it you`ll be taking the geometry from poor to at least indifferent. It can be made much better but you`ll have to spend on some new parts to do it. Mark SC&C