The ugly graph is meant to help with questions such as 35 vs 45 so you don't have to guess at it.
In the ugly graph for a 220AH bank the diff in time doing a 50-90 is 38 minutes between a 35 and a 55. So call it 19 minutes for 35 vs 45. But with one battery (call it 110AH even if it is really 85AH ) that would be 9 minutes of generator time saved for every 50-90. (actually less time for an 85 vs 110 of course)
So with those approx. figures, you can now decide what is "worth it" for your situation.
EG, If the 45 costs the same as the 35 and the 1000w can run it, then there is no value in choosing the 35, but there is the 9 minutes of gen time value in choosing the 45. Whatever.