53...technically a compact specific front derailleur would be ideal but believe my triple Campy FD which is sized/radiused in accordance to a 52 tooth big ring and can shift down to a 30T small ring without issue would work fine with limit screw adjustments for a compact double. My FD is a seat tube clamp design and can be scooted down the tube a bit for proper adjustment/clearance to the smaller diameter compact outer ring. My thought is to first try this arangement and if shifting is less than satisfactory, I would pony up for a compact double specific FD....a couple of tooth FD cage radius/arc difference shouldn't make much difference IMO...analogy being if largest outer chain ring of my triple didn't exist the triple FD shifts fine back and forth between 42 and 30T rings respectively with a full 10-22 tooth/radius cage disagreement. Where FD cage radius sizing becomes more critical is moving in the other direction...transistioning from a compact FD back up to a full size 53-54 tooth outer chainring/FD cage radius.

Grasschopper...I sent Gustav a PM and asked him where he found his Gossamer he just ordered as I presume he found a good deal somewhere. Don't know about the G2
however.
George