I'd figured that's what you were after, but since the radiator cools the coolant, and the coolant cools the oil, the D22 already does a fair job already.
If your engine isn't overheating, then it's doing exactly what it was designed to do and shouldn't need the extra cooling. If it IS overheating, since there are many, many other D22s roaming the deserts of Australia without issue, I'd be looking at a fault in your engine first, rather than putting an additional cooler in which would really just mask an underlying problem and could result in a catastrophic failure.
If you're just playing it safe and making sure that you're giving your engine the best chance it can of not having a problem (which has a caveat on its own) then by all means add the cooler. Don't put it in front of the radiator, because engine oil is very, very hot and the radiator doesn't need that much heat added to it. Put it in the airstream below the radiator if possible, but above a bash/stone plate.
The caveat mentioned: adding tubing, hose clamps and widgets to such a vital system like your engine oil circulation system will add a significant failure point. Things could go wrong with the cooler, with the hose clamps, with the hoses. If the cooler itself gets blocked by a thousand locusts it's no big deal because the oil doesn't NEED this additional cooling, but if the oil is pumped out of the engine because there's a split in the hose or a clamp has come loose, then it's a MAJOR deal.
Also, your engine oil capacity rises by the capacity of the hoses and cooler, so it needs to be accounted for in future oil changes.
You have to find the balance. The D22 is already a strong, reliable engine. It performs very well in the harshest extremes Australia has to offer. Adding insurance like this adds risk as well - is it worth it? That's up to you.
Personally I'm looking into a misting system for my intercooler which will just happen to help everything else as well - engine, gearbox and radiator cooling will all improve with it - without the risk of compromising the engine oil.