Both riders are understood to favour the new material, which offers stiffness levels of the normal aluminium design while saving weight.
Marquez revealed he had first experimented with it at the Valencia test in November, while Pedrosa had tried it previosuly at Sepang, where he set the fastest lap of the test.
Marquez said: "We are trying it at different circuits just a few times, not all the day, so we are able to compare well and decide well for the future because it is a new protoype from Honda and we are not 100%."
The reigining champion set the fourth quickest lap in the weekend's tests at Buriram and was again considered the rider to beat on race pace.
He said: "The bike is shaking a little bit more. Looks like the grip is a little bit better [with the carbon swing-arm], but then with the used tyre it’s shaking too much."
Pedrosa said: "It's quite a different thing. But it's just the first version so, also for the engineers, it's like a new style. We don’t have the experience with it yet and are just starting to get info about feelings.
"I've never ridden with one before. It's positive to have this new technology and Honda is working hard. That means they are willing to improve and help us, this is nice.
"There are positive and negatives but in general, it's a different character and for sure the first time you make one it's difficult to know if you make it correct, because the experience is not there.
"We will keep going to get more experience in the future.
"We first used it in Malaysia, but not a lot, so now we've tried it at two different tracks."
Aprilia is also rumoured to have a carbon swing-arm in the pipeline for 2018.
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