I'd go for 60 cm dried if I were you, or even higher as Goran said.
There's no such thing as too much cacti, high concentrated potent cacti is rare, and even with high quality and lots of material you'll have to consume as much as you can. It's VERY hard to get an heroic dose in your system, I'd have to say nearly impossible with home grown cacti if I may believe insiders.
But you can have a very profound experience if you take the time for fasting, and have TOUGH ENDURANCE to swallow, swallow and swallow more more more without puking. Eating 2 hours straight is no exception to me. Keep it in!
Laying down transfers you to your deepest desires and dreams while feeling sick and generally unwell. If you pass out and 'wake up' and start to take steps, you'll see why you went through all the effort. This bath, the melting lime and liquid like serenity is what your desires always were. You're a child that's jumping around as a fragile being with enormous inner realisation of empathy. Even stones have feelings, or sand. Your body is your self, you think with it. Everything is so bright with natural electricity. Green, green, green, dark green, light green, all appearances of green.
Mescaline trips are extremly tender, colourful and you'll notice how fucked up it is that there are cars in this world, you'll notice how wack all our food is! Even tap water may be dirty. Fruits are made toxic by modern anti-insect chemicals on it, you'll taste these.
By inhaling oxygen you might detect the microdust too that's going into your nose and lungs. The cactus diagnoses EVERY unclear detail in your body. Fuck meat, diary, cafeine, fats in the week prior to your experience.
Your stomach is going to have extreme cramps for hours but once these are over, you're truly safed from this grey world in which our minds are getting demolished.
When meditating, imagination comes very close to reality. Not just visuals, but fantasized imagination seems to get closer to a reality that is seen as sober reality.
Mescaline cacti are the plants from the deepest roots of mother nature and the universe. Regarding universal natural love, both mescaline and ayahuasca are our parents.
Mescaline is this kind of fantasy world to me:
http://www.youtube.com/watch?v=ihCMx-V6 ... re=related Cheesy now I watch it, but the world of mescaline differs with this distance from the sober life.