No, I haven't used them. I tried to email Nitromodels with questions about the metal arms here is the response I recieved.

"I am interested in your exi d226f servos. Do you sell metal arms for them or
will another brand servo arms fit these? Allso the servo torque is listed in
kg-cm 13 is this 180 inch ounces? Is there any reviews of these servos as I
googled it and could find nothing.

Thanks, Matt

Dear Customer

Please check our sites at that time to see if the items are available for ordering.

NitroModels Inc. "Where high quality models are made affordable" "

The response didn't answer anything. I would not use them without someone saying weather or not a metal arm is available for my application. As to how good they are? I don't know and seems as if nobody has tried them yet...

Good luck and let me know how they work out if you try one.