I got the information about the belly turret and the broom sticks from Doolittles autobiography, which for some unknown reason I failed to list among my references. On page 246 of the hardcopy he says, While the pilots were training at an auxiliary field, modifications were continuing on the B-25s at Elgin ..A major problem we encountered concerned the electrically powered gun turrets. The early B-25s had a top and lower turret with twin .50-caleber machine guns .. There were no guns installed in the tail section ..Much credit must go to Ross Greening for solving our armament problems. He suggested that we install two broomsticks in the tail and paint them black to simulate a tail gun position ..And since the lower turrets gave us nothing but headaches and were very complicated to operate, Greening suggested removing them. Again, I approved.
I read those pages again and the book (I Never Could Be So Lucky Again) seems to be following a linear time line implying these events happened in Florida. Any mention of Ross Greening doesnt show up until they are in Florida. But I think am also seeing the same things you are.
I found at least one other inconsistancy when I was checking about the guns again. His autobiography says the tank replacing the lower turret was 60 gallons and another source says 40 gallons. The book says the 60 gallon tank was always intended to be filled from 10 5 gallon cans loaded onto the planes, but Ted Lawson says all the tanks were topped off before they lifted into the air.