Graeme is right of course about what he describes. An Athena mech would of course be another solution but the spring tension in power shift compatible mechs is weaker than in ultrashort compatible mechs and long term that just means poorer shifting sooner.
I have one bike with a single ring and a 11-32t cassette with the shifting done by a Chorus 2014 rd. It works fine and the top jockey wheel tracks well enough. This would not be the case on all bikes though.
My race bike has the same setup but with 2015 record short cage rd. Again no real world issues although admitidly the shifting is better with a 12-27t but not my much. The problem the race bike has is torturous cable routing and thus has a bigger impact in shifting than anything else. To use a double though a longer cage is a must.
So it might be worth the experiment with the cage alone as it less expensive than a shifting bits but be prepared for it not to be the best solution. Second Athena mechs are not expensive and if it does not work well enough reassemble and sell.
Discuss light weight issues concerning road bikes & parts.