Asymmetrical Spinnaker Sizing?

[bluewater]

We are thinking of adding a used Asymmetrical Spinnaker to our sail inventory and wanted to see what people think of appropriate dimensions.

Bluewater's stats:

Headstay: 47.5 ft
I: 45ft
J: 15ft

So my by understanding we want to find a used Asymmetrical Spinnaker that has a foot of 24 - 27, but what about Luff? The best advice I have found is that we want a luff as long as possible with out the sail dipping in the water when it has collapsed. So any advice you have in that realm would be greatly appreciated.

Also, I have found a AS with a luff of 47.6, foot of 33 (But that is a 220% J!) To big? We are currently coastal sailing, so we are not concerned with needing to downsize a bit for night time passages, as we are not making any.

I would appreciate any thoughts you have!

Michael