Nope, as long as you can keep your balance not not hinder the horse during the test, don't try and go for dressage length stirrups in a jumping saddle though
They would definitely be affected due to a different seat and position. If you’re just doing 4-H or local shows, I don’t think you would be marked down, but if you’re doing A rated dressage shows, then definitely
no. Your marked on what your horse does. my marks haven't improved because of a dressage saddle. Your should have natural balance and strength in you lower leg. aVERY expensive dressage saddle shouldn't help.
Yes because your position in a jumping saddle is different to a dressag saddle:)
Yes because your position is different in a jumping saddle
Your position would be different in a jump saddle to the preferred so id guess your position marks would be affected