WOW  Ed, I’m impressed.  I wonder how many can honestly say they go to this level of detail on their annuals? 

Mark

I stick a small "Inspection mirror" up  through the AN-16 fitting with a small light shinning on the mirror. (I think next time I will wire a small LED to the head of the mirror - would make it much easier)   I then run the mirror up and down the side tank and rotate it at intervals looking mainly at the condition of the small 1/8-1/4" dia cross tank tubes.  I look for blockage or any indication of scale/gunk.  Thus far I have found none.