I have taken the liberty of copying and pasting below a post by Tramper Al from the specified forum; here it is.

I've tried to make this point a couple of times in the midst of a heated "Is this a good time to buy TIPS" thread, but generally been ignored. May I try again?

It seems to me that TIPs are a CPI-indexed product and that the bond market knows this very well, and thus offers me exactly the real rate on TIPS that it ought to, given the market's CPI forecast and an insurance premium

But the CPI woefully underestimates inflation, you say? Or your personal inflation rate, or whatever?

If TIPS were instead indexed to a different, or a better, or a bigger indicator of inflation, would that really matter to me, buying TIPS?

For example, say the Treasury came out with Double TIPS, that were indexed to 2xCPI, that is twice the current index. The bond market would understand this, charge a premium based on it, and then offer me a real rate accordingly, yes?

Or a health care inflation index could be used. Or food + energy only, or whatever. What would it matter, if the bond market is efficient and I don't presume to have inside information?

So I guess my point is this. It is the collective bond market that determines what I'm going to be paid for owning TIPS, not the Treasury or the Government in general. And it does not particularly matter what CPI is, as long as there is a collective knowledge as to what it is and what is expected of it.

If you want to read the entire thread - it is short as of now, you can do so via this Link 

Ray