Imagine a beastmaster ranger halfling who mounts his giant wolf spider beast. The giant wolf spider has the spider climb feature, which allows them to climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.
Can a giant wolf spider climb upside down while being mounted? This is a tricky question to me, since I imagine the halfling and his gear would weigh 100-250lbs. Do I simply use the carrying capacity of the spider (15*12STR=180lbs?) and the type of surface is irrelevant? It seems strange to me that a giant wolf spider could be upside down on a smooth surface with 200lbs on his back.
I am the DM in a 5e campaign. Also, I should add that I’m also curious also about wether they can climb along a vertical wall while mounted, which should be easier than upside down.