Tom,
Kit Car Mag. did a drive test on a Vintage in July 2004 (not sure which issue it came out in), and was referred to in the May 2006 Issue (p.45) in comparison to Thunder Ranch's RSK.
Overall though, realize that, like the original Spyders, each replica is very unique. . . performance numbers for one will have little correlation to another (even within the same manufacturer). Differences in powerplant, tranny, suspension, etc. will all impact performance of each and Vintage is known for its quality one-off's and custom builds.
The benefits and limitations of these machines are their light weight (it doesn't take much for them to get goin, but if they get goin too fast, they will fly. . . literally). Also, due to their small size, it is challenging and sometimes impossible to get larger displacement engines in them (which isn't an issue since these larger engines actually detract from their performance).
Hope this helps.