Matt....As stated in the earlier thread, once the plastic tanks start to leak, it's best to replace the radiator. I don't know if you're looking for a temporary fix or not, but patching it is tantamount to playing with a time bomb.
BMW V8s, for emissions purposes, run hotter than the six cylinders. Prolonged exposure to upwards of 105+ degree coolant (on hot summer days) compromises the structural integrity of the various plastic parts. This is why, in the common case of an M60 expansion tank blowing up and the engine overheating, practically every plastic part in the system has to be replaced. Weight benefits aside, plastic just doesn't do the trick as a reliable long term cooling system material.
So, patch the radiator if you don't mind the possibility of getting stranded. Otherwise, and I have to be frank about this -- don't be cheap about it and do it the correct way. These cars don't like half assed repairs. (In fact, I had one of mine fail yesterday on Fritz)
best, whit