Replace the 42 with a 40, for a perfect 1.5-step pattern: 52-40/14-17-20-24-28. I use a slightly tighter version of the same concept: 50-42 / 14-16-18-20-23-26. Normally, one shifts by one rear cog at a time, which skips over one ratio, e.g. 4th gear to 6th. (Pattern is 1,2,4,6,8,10; 3,5,7,9,11,12.) To fine-tune upward by one ratio, you have to remember that the front shift covers three ratios at a time, whereas each step in back covers two. To shift up one gear, you either have to add 4 and subtract 3 (if coming from the large chainring) or subtract 2 and add 3 (if coming from the small chainring). Trust me -- these shifts become second nature after awhile.