I wouldnt be too worried about scratching a new bike during a test ride. the shop can easily return it to the mfg if its damaged. with that being said, ride as many as you can. if a shop doesnt offer you a good long test ride, go elsewhere. you can even bring your own pedals and shoes if you ride clipless. if the testride feels weird most shops will swap stems with another bike in stock so you can try different lengths and angles, seats too.
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2010 Kestrel RT900SL, 800k carbon, chorus/record, speedplay, zonda
2000 litespeed Unicoi Ti, XTR,XT, Campy crank, time atac, carbon forks