Congrats! What an example of perseverance !

(For novices it would be nice to know an explicit formula linking the small numbers to the big number....)

Also, nice Cunningham chain of length 6 - and you would have qualified even by counting it only as 1!

Retrospectively, wouldn't that have been an efficient sieving criterion ? (By requiring to have a chain of length 6, you can advance in steps of 6 when scanning n-values. But I don't know if one could expect a candidate with the chain [2,3,4,5,6,7] - what's the relative frequency of such among "good candidates" ?)