Put all of the parts in or don't put any in. There's been a lot of thought and testing into the kit. It's a system. I once had a guy come back to me complaining about the rotten kit I sold him and how it @#%^*@up his valve body. He ended up with 2nd, neutral, reverse, and park only. When I looked into the box he was returning, there were a lot of parts in it. I asked why he didn't install all of the parts as per the instruction sheet, and he told me his buddy (who wasn't a trans builder) said they weren't required. Unless you're a qualified transmission builder, or your "source of information is" and have an understanding of how the hydraulics work in a transmission why would you not install the kit as per the instructions. All kits work, some better than others, but all kit manufacteurs have spent a lot of time and money to make the kit work as it should.
just my $.25 worth