I tried several PFD's and found almost all of them very restrictive, consequently my race performances against my usual markers were poor when compared to usual weekly time trials without PFD's. I have finally settled on a Think PFD, it doesn't have all the bells and whistles hanging off it that others do which seems to reduce the bulk and is the least restrictive version I have tried thus far. There was a lengthy debate on this site regarding the virtues or otherwise of a built in water bladder pouch which is absent in this PFD (which I won't go into here as it just got plain ridiculous). Suffice to say although the Think PFD doesn't have one my requirment was for minimal bulk and this didn't bother me in the slightest. Not sure what country you are in but Stew O'Regan can sort you out with one if in Aus.
The other option which I see in my work environment but less so in SKI racing are your 'horse collar' style inflatable PFD's which are activated when required with a small CO2 cylinder. I have worn these at work, they are very light and generally toggle operated (self operating ones which are activated by salt water would clearly not be suitable for a surf ski). The only issue I see with these style PFD's is that if you hit your head falling from the ski and are unable to operate the toggle they will it will be of little use to you. In any event if you simply cannot get comfortable with a standard PFD, this may be an option these types are approved by most international and local maritime authorities and are certainly preferable to solo paddling off the coast 'sans' any approved device.
Good Luck with your search.