Ok, so I’m devising a kind of crazy plan to get another Marriott card, and need some help.

First, what I have:
- Chase Bonvoy Boundless (bonus received far more than 24 months ago) - AF early March
- Amex Bonvoy (old SPG, so bonus more than 24 months ago) - AF late April
- Amex Bonvoy Brilliant (opened in March)
- 5/24 slot opens late April

I want to pick up another Boundless, and upgrading to RC has been on my radar.

So I am thinking of upgrading the Amex Bonvoy ($95) to another Brilliant shortly before the AF (in theory, this should cost me a pro-rated fee, but give me a 85k cert).

I’ll also need to upgrade the Boundless to the RC, but I’m confused on timing. If I PC to the RC before the AF, I understand that I will get charged a non-prorated AF. But if I do that right before the AF, then do I get charged double? If not, how long is that window? Could I do it in late Dec to get the extra travel credit?

Also, if anyone wants to shoot holes in my plan go ahead.