Bareback Horse Riding

 
It'll give the slowness effect with 'shouldReceiveSlownessDuringRidingWithoutSaddle' enabled:

 
Or occasional damage with 'shouldDamageDuringRidingWithoutSaddle' enabled:

 
Wearing leather pants will prevent the slowness/damage from happening. It does use durability:

 
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For issues, ideas, suggestions or anything else there is the Github repo. Thanks!