We generally do not wear any gauntlets under the pants of the suit. The stuffing inside a bite suit is more than likely polyester filling.
I do wear neoprene gauntlets on my arms when decoying for our Patrol dogs. The neoprene gauntlets are like the arms from a scuba suit. I wear a Demanet competition suit to work Police dogs. Your going to get bruised, cut and it is going to hurt after a few dogs. All part of working dogs. While I have taken some hard leg biters, I've never felt the need for Gauntlets for my legs. Knee bites hurt, but the legs being thicker and getting dogs to bite full reduces a lot of the pinching.
IMO, just suck it up and enjoy the feeling of a strong dog biting really hard. Feeling the pressure is good for the dog and good for the decoy.
“Beware of false knowledge; it is more dangerous than ignorance”. George Bernard Shaw