with 1Mk/s i have a key off 66 puzzle in max 10 days
with 300Mk/s i have a key in 10 hours
if albertobsd want work with me, we can make a call and divide 50/50 the 66, 67 and 68, maybe more
I think that your calculations are some wrong, what formula do you use?
According to my research with 1 Million keys/s the puzzle 66 can take up to 1 million 169 thousand years.
This is the secret, all the techniques that have been tried will not solve 66 onwards, but we can work with my strategy, with a good enough rate even the first blocks wallets can be broken in months.
I assume you try to filter out all privatekeys that do not seem random enough. Like repeating patterns in any base (...1111..., ...2222..., ...1234...). This will reduce the searchspace. But I think the benefit will also decrease exponentially, so you will have to search like 65.5 bit instead of 66 bit for 66 puzzle.