Larger jump becomes easy with a Schlumpf Speed drive crankset ..
that 39t chainring X 1.6 [its overdrive ratio] is 62,4 'teeth',
a 38 x 1.6 = 60.8,
but the chainring is still physically the smaller size.

the shifter, is a button where the crank bolt cap is, passes thru the BB,
so protrudes on 1 side, flush on the other, you tap it with your heel.