Yes that's the only sure way. I tried the Plus Six for size at the Festival of Speed Goodwood and the only thing I found being tall was that you sat fairly high in the seat but it felt comfortable enough and they do look very similar.
I had a great experience with Henry when I bought my new Sport out of his showroom 2009 in Bristol before they relocated.
Impeccable service including all the warranty work that was needed with this new model at the time including three stress fractured windscreens and numerous bits falling off that had become unglued.
Sorry to hear your experience of purchase was not similar to mine Dave.
