Hi fixj - congratulations on the weight loss. [I have managed to lose nearly 30lbs (with lots of help from my wife after a high cholesterol score) and certainly enjoying my new bike.]

Not entirely sure how to apply your advice re 'crossover' gears on my three-front-crank' set up on my 2012 model. Perhaps I am getting a little too detailed when I should be out doing a longer run than the 30 km I managed this morning, but I have tried computing the gearing ratios in table below. Currently I would not use these gear combinations - are you suggesting I should extend the 'do-not-use' combinations (eg those indicated like this 50 39 30
12 4.167 3.250 2.500
13 3.846 3.000 2.308
14 3.571 2.786 2.143
15 3.333 2.600 2.000
17 2.941 2.294 1.765
19 2.632 2.053 1.579
21 2.381 1.857 1.429
23 2.174 1.696 1.304
25 2.000 1.560 1.200
28 1.786 1.393 1.071

Not very talented on computers, finding it a challenge to get the table columns to align. Hopefully you can see that the 1st row is # teeth on the front rings, and the 1st column is # teeth on rear cogs. The cells are then intended to represent the ratio of front divided by rear.