Interesting call. Looking at Sharky 775 heat meter questions - #23 by Zarch, how about a simple up and over loop of pipe. Halfway along a tee, up to a second tee off to to left for the expansion vessel (lifted up) and straight up for the AA valve (and give it a bit of pipe as well).
Probably improves the flow (not turning on 2 tees). Should still allow the air to rise.
Personally, I’d do a radius bend, but Plumbers seem to be adverse to bending pipe these days.
[edit]
I notice @glyn.hudson setup, the AAs are Tee’d off a horizontal pipe. Samsung Air Source Heat Pump Installation with monitoring - #6 by glyn.hudson