No, Benny is correct. You could have invested 50% initially in McGrath as triple stress, and made changes to the other 50%. But once you chose to invest 100% as triple stress in McGrath it is all locked up until the end of the triple stress period.
For those Gamers who haven't worked it out, there is not much to be gained by putting 100% in a stress option, when you get exactly the same bonus payment for only locking up 50%. It was set up that way deliberately so that Gamers didn't have to lock up all their money to get the bonus payment. Also 50% splits lessens your risk of 100% of your money getting hit by an unexpected injury.
I also should add that the stress options were designed in a way to be much more beneficial to Gamers at the bottom of the table, than those at the top. So I am a bit surprised that stress options are being used by the wealthy leaders, while many Gamers with not much panic dollars are ignoring stress options.
For example if you only have $100 a 50% split on first-picked, low risk players like Heppel and Zerrett for 2 or 3 weeks will get you a much, mutch better return than trying to pick an outsider who might get selected at $10 return.