Should I apply pressure on the saddle during downhill on a rigid frame It is known that, while climbing, one should apply consistent and maximum weight to their saddle, in order to have precious rear tire traction.

The other day I was going down a dirt road, and the road irregularities and scattered stones, bounced the rear wheel maybe  up to 15-20cm in the air. My concerns are two:


loss of rear traction, while the wheel is in air
the saddle hitting me from behind, and throwing me over the handlebhars.


Should I attempt to apply some pressure on the saddle? In what way?

For example, I imagine that I can close my tights, thus clamping the seat and having some control over it.
No. If you sit on the saddle then you become connected with the bike. That means that the next hit from the ground will be transmitted as is on you and you'll most probably go flying in an uncontrolled manner, usually nose heavy, and you don't want that.

Apart from getting rest or pedaling, the only case where you touch the saddle is with your inner thigh (one, not both of them) in some offcamber cornering scenarios. But I think this is irrelevant to your question.

General rule for descending on rough terrain is:


heels down, applying max pressure on pedals (that's for flat pedals)
body in attack position
hands relaxed, ready to act as suspension
knees relaxed, ready to act as suspension
stay low
look ahead, not down to your front wheel