My slave wanted so much to please me but was not certain that he could take the full force of my kicks. So he requested to be put in the suspension harness with a leg spreader on to keep his legs wide apart while I dealt with his balls. One hard kick to the genitals would have made him fall to his knees begging for mercy but, with the suspension kept him upright and the spreader bar keeping his legs in place, psychologically he felt that he could take more. I must say afterwards he was very pleased with himself, even if was nursing a pair of very tender balls!
Whipping a slave tied to a cross is possibly the epitome of the SM in BDSM. It can be the most intensive form of play for both the Dominatrix and slave and a leather whip can produce a range of sensations from sensuous right up to the extreme. For many subs it can get them into that glorious sub space quicker than anything else. However, like most things, you either love it or hate is and some just never enjoy the sensation.
Fortunately I have a slave that enjoys the whip and makes the most wonderful noises as it falls on his back.