Castor correction plates

I've previously mentioned that I have a 4" front lift and 5" rear lift (but with a lot of weight it looks level) on my 2000 GU. I've also said that there was nothing done about castor correction etc with seemingly no ill-effect on steering, handling, shuddering etc.
However, there is an obviously noticeable angle on the front uni-joint because the front diff is angled quite a bit. So I've been wondering about fitting a set of these castor correction plates. Looking a photos of them, it is obvious that new holes have to be drilled through the brackets which are welded to the axle tube onto which the factory trailing (or is it "leading"??) arms are attched. It looks like the original rear hole is used for the plates, but a new hole quite close to the axle is needed.
Has anybody had any experience with this fitting (I think the 80 series cruiser is the same set-up)?
What bothers me is that (a) the hole is quite close to the axle tube, so it might be difficult to get an electric drill to get a large enough hole parallel through the 2 sides of each bracket & (b) on the driver's side, the diff pumpkin prevents drilling from that side, so the drilling would have to be done from the side near the disk brake rotor. I'm thinking that it probably requires the use of a right-angled air-powered drill.....
Any thoughts?

Cheers,
Roachie