EDIT: In a one-year review of his Power Wagon, a guy was able to fit a 35-inch Falken Wildpeak AT (35x12.5x17) in the spare location by
deflating it. Go to 9:30 in the video to see the spare tire info:
NOTE: In my earlier post, I mistakenly attributed this to Brad from Trail Recon - I apologize for getting the two videos confused.
As you probably all know, not all 35s are the same size; here are some popular ones with specs from:
https://tiresize.com/
Falken Wildpeak A/T3W 35 x 12.5 x 17 is listed as 34.8 by 12.5
BFG KO2 35 x 12.5 x 17 is listed as 34.5 by 12.5
BFG KM3 35 x 12.5 x 17 is listed as 35.0 by 12.5
Cooper ST MAXX 315/70R17 is listed as 34.6 by 12.8
Nitto Ridge Grappler 35 x 12.5 x 17 is listed as 34.8 by 12.5
Nitto Trail Grappler MT 35 x 12.5 x 17 is listed as 34.8 by 13.2
Toyo Open Country MT 35 x 12.5 x 17 is listed as 34.8 by 13.2
According to this site, the Falken Wildpeak AT is a tiny bit taller than the BFG KO2, and the owner in the video fit the Falken in the spare location deflated. That suggests that the KO2 would fit, but I wouldn't trust these measurements 100% - so try fitting a tire before buying five of them!