Baggies. Is it even possible to go fast enough through technical trails where there’s any wind resistance?
I’ve worn tight synthetic tops on hot days, what I can’t stand is the feeling of the mud splashing up on those thin synthetic layers, crusting, and then mixing with sweat and osmosing through the layer and creating a shitty layer of muddy itchy sweat. My Fox shorts with butt pad shorts underneath are super comfy, give an extra layer to stop the mud from wicking through, and also feel better during the occasional crash.