While I don't have a Kapex, I have just recently built one using Incra Track and Phenolic Ply. It works great.
I wanted to buy a Sawhelper, but they don't seem to be interested in selling their product. It took two weeks to place the order because of lack of response. Once I placed the order, I was told that I could expect a call in about 6 weeks to get the payment information. I am about 4 weeks overdue for that call.