I plan to transfer about 244k points from AMEX to Payback and then to MM.
Do you guys do such large transfers before? I only converted less than 100k until now, and I am concerned about hitting a cap and being unable to proceed as planned.

Now, I am fully aware of the 75k cap regarding the additional miles, but I guess I am just below that.

Can you please confirm such a (large) transfer is within the rules of Payback and MM? I don't expect Amex to object to this, but I don't want either to be stuck with 100k payback points and unable to transfer due to some obscure rule.

I also know precisely what I'm about to spend them and found the award flights - I only hope they'll still be available by then. And I know the bonus will be credited much later, but I expect the regular transaction Amex > Payback > Miles to take less than calendar 10 days.
I'm hoarding the rest of my Amex points for next year.