Depends how you look at it, in SWIMs experience, it is more about meditation and integration that takes place before and after the journey. I have been locked out of hyperspace for extended periods of time untill I learnt the lesson behind what I had experienced before.
PLUS
27mg is not a huge dose dude, how are you smoking it? if its in a normal pipe or bong i'd say step it up to 60-90mg of crystal on top of changa if you want.

happy travels!