Job well done! Like you, I also converted to the eTap approach of shifting on my Di2 bikes. It is wonderful. And, what I really love is that the left hand is always easier and the right hand is always harder. And, unlike eTap, we can change the big ring with one hand (a plus on fast approach uphills).
Furthermore, with semi-synchro, I never need to use two hands at all. Changes to the front mech automatically adjust the rear mech 2 cogs for me. Brilliant.
One quirk: as some may know, the shift to the big chainring is seamlessly paired with an instantaneous and "subsequent" shift to the rear cassette. BUT, the shift to the small chainring is a bit jerky. Instead of shifting the rear cassette first, it shifts the front mech first resulting in too quick spinning until the rear moves. I've adapted to it, but i'd prefer it to shift the rear first (as I have always done prior to synchro) and then quickly drop down into the small ring on the front mech.
Anyway, a nice improvement that hopefully a modest software update can address soon.
And if you’re interested in altering the shift levers to behave similar to SRAM eTap shifting, I have another doc for that: Shimano-eTap shifting