Originally Posted by Doge

Chains drop off big rings with no shifting. Bumps and corners and out-of-the-saddle sprinting can do it. Off round rings do it more.

As I mentioned - this is now racing - TT. I've never used a double for a TT bike for me, wife or kid - or most team bikes I've built. So the bikes are setup that way from the start. The FD is used as a chain catcher only.

There is conflicting data but the thought is bigger-bigger is better than smaller smaller. So 52X14 is better than 45X12 (same gear). There is less chain tension and better chain alignment. If the ride is going to take place on a ~100in gear (52X14) then it is better to get that 14 more toward the middle, or whatever cog will be used toward the middle. All this stuff amounts to maybe 2-3W but TTs often have places split by 1 sec.