Python Script Tool Validation errors

I am currently creating a python script tool at work that works fine, and could be even more polished if I can get certain functionality working using the tool validation. I am trying to get the tool to recognize what the the geometry type of the first input is, and based on that, set a parameter further down as a required parameter if its a "Polygon", or not required if it is a "Point". Here is my code so far:

import arcpy

class ToolValidator(object):

def __init__(self):
self.params = arcpy.GetParameterInfo()

def initializeParameters(self):
def updateParameters(self):
if self.params[0].value:
desc = arcpy.Describe(self.params[0].value)
feature_type = desc.shapeType
if feature_type == "Polygon":
self.params[7].enabled = True
self.params[7].parameterType = "Required"
self.params[8].enabled = False
self.params[8].parameterType = "Optional"
elif feature_type == "Point" or "Multipoint":
self.params[7].enabled = False
self.params[7].parameterType = "Optional"
self.params[8].enabled = True
self.params[8].parameterType = "Required"
def updateMessages(self):

I have gotten it to recognize the geometry type of the first input once someone sets it. When its "Polygon", it will disable parameter[8], and when its "Point", it will disable parameter[7]. My problem is with with trying to toggle the parameterType property of a Parameter object, as suggested http://resources.arcgis.com/en/help/...00000063000000 here. It says that the parameterType property is both read and write using tool validation. For whatever reason, I cannot get it to work. Ultimately, if the input geometry type is "Polygon", I would like parameter[7] set to parameterType "Required" and parameter[8] set to disabled. If the input type is "Point", I would like parameter[8] set to parameterType "Required" and parameter[7] set to disabled. Any help is appreciated.