Hi Paul,
I bought an asymmetric spinnaker in June this year. I got a quote from Kemps which was very cheap compared to Quantum, almost half price, but when they started asking me for dimensions of the boat, I got a bit worried that they were not sure about the details. After speaking to Bill Parker, he advised that only Quantun have taken the trouble to actually make one, try it out on a boat and adjust the design to get it right for the 235. In the end we bought a Quantum one and it is great. The price difference is considerable so it may be worth taking the chance. You pay your money and take your choice.
Graham Ebb
235/25 Blue Jazz