Sphinx,
If you are seeking intense cramping, please try this. I know you are an experienced klismo, but I'll add some newbie-cautions for those that aren't. First of all, thoroughly clean out your colon, so you don't have to deal with the smelly brown stuff any more.
Set up your bag with a trickle-clamp, and before insertion confirm that all air is out of the system and that you have a steady drip-drip-drip coming from the nozzle. Fast drips, not a stream.
Fill the bag with cold water from your refrigerator. The 40 to 45-ish degree temperature of the fridge works better, I find, than true ice-water with cubes floating in it, though both will work. Hang the bag high.
Have a source of immediate replacement heat, like a warm electric blanket or a hot-water bottle. Please don't ignore this step.
Lie down where you are comfortable, as this will take a while. Lube, insert, open clamp to the drip position, and lie back. Snuggle up to your heat-source and check your watch and wait fifteen minutes.
I believe you will then be experiencing the sensations you are seeking. Whether you interpret those sensations as punishment or orgasmic ecstasy is up to your mood of the moment. :-)
Hugs,
Diane