Running Di2 wire between shifters in aluminum Zipp bars

https://www.sram.com/en/zipp/models/hb-dbsc-sl7x-a2

I have these bars and want to install on my 2021 Roubaix Expert with 11 speed Di2. The junction box is in the down tube. I figure one Di2 wire will come up with the brake hose to the right shifter, then I need to connect the left shifter to the right shifter. The bars have small holes on the bottom of the drops on both sides.

What's the best way to do this? I could run a shorter cable under the bars which would be mostly covered by bar tape (except under the stem). Otherwise, I think I'd have to run from the left shifter, down though the left hole, through the bars, out the right hole, and up to that shifter. I check with a piece of string and that'll take a 1600mm wire.

I'm coming from carbon bars which had much better access holes so I'm note sure how best to proceed with these Zipp bars.

Thanks!!