Not so much a case of "wouldn't try it" but more a case of, "it can't be done!"
The 300C is flown from the left seat which means that with dual controls taken out, you can get two passengers alongside (if they don't weigh too much!). However, the CBi is flown from the right seat and with the collective in the middle, three across is no longer an option and there is no third seat.
Sorry to say but you are wrong mate. I have done commercial work in the 300c and 300cbi and they are both flown from the left seat. Both of them have the extra seat in the middle when you take out the collective. It is also possible to carry three people in the cbi if they are not to heavy, you are limited with the amount of fuel you can take, but it is not impossible.