I also had creaking issues when cranking hard standing up, I found the bolts were topping out on the t-nut as they are too long
The captive nuts have almost 2mm at the end with no thread so I took a file to them and removed 1.5mm of their length so as not to mess with the threaded section. I also used normal steel chainring bolts as the ones provided are not thread all the way to the bolt head (this probably isn’t required if you file enough off the captive nut).
Cleaned and put a bit of grease on the mating faces of the frame and swapout and then did them up, I could instantly feel the bolts tighten up loads better as they didn’t hit a hard stop just got hard to torque, also the captive nut didn’t spin as they got tighter as they were actually being pulled tight into the swapout seat.
A 10 minute job to sort the issue once and for all