The two-time champion tested the bike, and its factory equivalent, as part of his ongoing development work with Honda.
And while rain meant the first day was entirely washed out, Stoner said his day two running was easily enough to convince him of the production bike's potential.
"Unfortunately the weather played a big role in this test which was a little frustrating not to be able to share the workload over the two days," Stoner said.
"We tried the production bike which was more impressive than I predicted.
"It had a similar feeling to the RCV [factory bike] but with a little less power and a different feeling in engine braking.
"With some small modifications I believe this bike will be competitive and I look forward to the next test with it.
"In general it was a good, but busy day."
Stoner said he had also helped Honda evaluate some substantial upgrades to its factory bike, adding: "We started with the current RCV, trying to find a base setting and then work from there.
"We had two variations of chassis' to try and some big modifications and improvements in my opinion."
This year's current Moto2 points leader Scott Redding signed a deal to race Honda's production bike run by the satellite Gresini squad next year.