I know its been said already, but roads differ, and I wouldn't worry what Kershaw's did or didn't show. The key thing is that you use the same one every time after making mods so that you can see the difference made. Treat your first session simply as a bench mark.
My Sud has been on one road that showed 145 bhp at the wheels, on another it showed only 105bhp. Realistically we reckon that it has between 20 and 25 bhp more at the flywheel than a standard 1700 8v boxer (which is 118 bhp), hence has about 140bhp at the flywheel.
The guy who built the engine reckons on losing 20 to 25 bhp to the wheels, however this is affected by ambient temperature, and more so tyres. You could put a car on the rolling road on one set of tyres, and get 5 or more bhp either way on a different set. Tyre pressure affects this also. Additionally, engine temperature, my Sud loses 6 bhp at the wheels when at max temperature, so if some of you had your engines running hot while waiting to get on the road, you might have seen less power than someone else who was at 70 or 80 degrees.
Remember that manufacturers will test for and quote figures obtained under optimum conditions. So long as you all had a good time at Kershaws, then don't worry about it.