At one time I thought about doing a crawl-through tunnel, but decided that for the real effect you have to be standing up and built a big one. The idea is to make those passing through so dizzy they want to fall to their knees.
Of course if that's all you can afford to do I am sure those who attend will think it's pretty cool. You will want to expirement with the rotation speeds. Probably faster than a full-sized tunnel but possibly slower. Putting a spinning disc just past the exit will also help heighten the effect.
To increase the scare factor, you should think about putting something on the inside besides the normal dots, spirals or lines. Some of the manufacturers have vacuum-formed panels with skulls or other things built in.
Hope that helps somewhat.