Hi.....Your numeric correlation is basically correct. I find 1, 2, and three to be plentiful. 4 has been tough. Five seems to break the streak as, for me it has been easier, akin to the first three. 6, 7 & 8 are tougher, with 7 being ever so slightly easier than the other two. So speaks one collector in Florida......
However you chose to go about it, unless you are prepared for a slow slog with lots of down time, a looser level of acceptability is in order. The Red Borders chip easily........ Good luck....I have been chasing it since the T206 dried up for me over a year ago. I have reached 140.......