I'm not sure where exactly the would build up callouses by looking at the device, but I'm sure each one if a bit different. I would try brace wax or cigarette paper (saxophone hack) if it's causing issues.

What "unhelpful" said could be on option. I would be very careful though. I only assign students to double reeds if they have an interest in learning those instruments and understand the challenges of them.

I would never assign either based on physical need alone. But that's not what Unhelpful was really saying either.