Hi Sailwave,
I hope you have read most of my F16 oneup thread before making this decision. I know it is lengthy, it's been going for a while.
You are going through many of the same thoughts I did, except I couldn't possibly live without a spinnaker!!!!!!!! I believe it is difficult to get a one up boat to go as fast as a two up boat but the A class in Australia show it is possible. They are at the front of the fleet even in the strong winds, against F18, Taipan sloop etc.
So my answer is to use thier one up refinement for a F16. I believe for a oneup to go straight up against a two up it must have everything in it's favour as the A cat does minimull hull etc. Not just a two up without the jib. Pity it's to early to tell you the result of my experiment but in the next few months hopefully I will know.
Believe me I wouldn't be sailing F16 if it wasn't the most fun you can have on the water and the physical challenge of sailing one up with the spinnaker leaves anything the A has to offer for dead.
Regards Gary.