Never suffered myself, but usually know when the season starts as my relatives who do suffer keep asking for 'discounted' hayfever remedies from my current employer (GSK). One of them had some sort of implant done about 3 years ago, and seems to work well in reducing the severity of her symptoms - don't know any details of it though.
Don't the roadsters come with pollen filters - or do you need to have the roof up for them to work?