Moto Guzzi mysterious oil leak............another porous cylinder head !

A month os so back I posted a series of pics showing the left hand cylinder head from the Bronze Guzzi Cafe Racer that had a very small hole in the casting causing a hard to detect oil leak, and when found, what was actually done to cure it. As I sorted that one out an even more minor leak had developed on the r/hand head,which originally I thought was going to just be the rocker box gasket - bearing in mind that this head had been on the bike for at least the past 8 - 10 months with no problems at all. My friend Martin offered to take it to work to get it crack tested,but as I was impatient I just thought that I have three other clean r/h heads - none of which were of a pair - all with good guides in place. To cut a long story short after sorting out some valves and springs I had the seats re-cut and I couldn't believe it when this also had a very small leak. This again took some time to detect, though with perseverance and a very handy inspection light tool  the tiny hole was finally found and welded up and now all is good !
   On reflection, I think that why I have a number of porous Guzzi heads amongst my stock of parts is because of a bulk purchase of some ex Italian bike dealer stock - mostly Guzzi - that I made some 15 years ago. Somebody in the Trade,working on bikes day in day out, is going to come across this not unknown problem possibly a number of times,get fed up with trying to find the cause of the leak and then just swop heads and put the leaky head away to be sorted another day. That 'other day' just happened to be 15, 20 to 25 years later.............

The culprit is circled just between the top two fins

And on the inside,but ignore the two to the left

and wasn't I the LUCKY ONE !! 
  Now,with a new rear tyre already fitted, I can think about advertising the bike For Sale,but I'll be very sad to see it go as it's been Bloody Good Fun !