joe, with regard to your original post about how to price a hard top, I think that demand would be pretty elastic--the lower it is priced the more speedster owners will buy it. My guess is for people who are not price sensitive and very interested in a hard top option, they would have bit the bullet on a custom job or simply bought an IM to start with. The other factors that would impact sales are the intelligence of the design and the marketing.
For example, I would be inclined to pay more for something like what jogyver has pictures of in his photo section. www.speedsterowners.com/files/view.asp?sf=Jogyver&f=newspeedster13%2Ejpg
This design has a more modern look than some might favor, but with this hardtop, form follows from function in a way that I think Mr. Porsche would approve. First notice the way the top extends down on the window frame at the front corners which helps deflect wind and water from the side curtains. This design makes it much easier to cut a pair of side curtains (or windows) which won't leak in where the windshield meets the soft top. Second this design incorporates a "real" glass window that is apparently readily available in in UK junkyards. I don't know what the US equivalent real window would be, but obviosly if a $20 rear window from, say, a Ford Escort can be popped in there, it will allow a superior product at a lower cost--meaning more sales. Third, this top has a middle section that comes out for targa driving. This feature differentiates your product from everything else on the US market and will increase sales.
Finally intelligent marketing is a key to selling these tops. The ability to provide potential customers with precise measurements, step buy step instructions on how to fit the top to their car posted on the web, and details about how you have a no-hassle means of shipping the tops, means more people will be willing to buy the top on the web. This will not only cut down on many individual calls about "will this fit my car? and how do I fit it?," it will also cut down on your sales cycle because people have all the information up front to find and buy the product on the web without leaving it until they can arrange a trip to your neck of the woods.
I would encourage you do pursue this project. I don't want to have to get some big pieces of foam insulation from home depot shape the perfect top like a surfboard and lay my own fiberglass. If I can buy something that is remotely close to what I am looking for at a decent price I would do so happily, and I expect others would too.