I have not as of yet tried running with my AS as of yet, spouse does not even want me out by myself sailing with main and
jib, much less the Chute up. BUT, that is neither here nor there.
What I did when I bought my AS ie asymmetric
spinnaker. I choose to go with one about 85% of max size. For more than one reason, biggest, I ha never flown a chute before. Next, while interested in ncreasing downwind performance, I was not worried about the last nth of a knot in speed. So I gain about 1-1.5 knots vs 1.5-2 knots. The sail downwind is much more pleasurable than with a main and genoa alone!
Size wise, with my 30'r, max Symmetric is around 700-720, AS 680 or so, my sail is 590'ish. In the mean time, since I am racing a bit more than I thought I would, one of my next sails after a new main and 155, is a 700# symmetric for these days, the AS makes a good high wind, ie up to 20-25knots with crew, up to 12-15 knots just spouse and I sailing downwind sail. the bigger symmetric will get me to about 15-20 with crew on board.
Not that my way will work for everyone, but for some, going with a smaller chute will lower some of the broaching issues with a slightly larger sail, sailing alone or with smaller crew size. I would think if I was in Alex's shoes for example, with family onboard, a 1200# chute vs the 1500#'r, would make life fun downwind, but still manageable to a degree with just him and Fred running the boat.
Take these comments for what they are worth on your puter screen! Not much, then again................
marty