TIP$TER is an extremely useful tool for planning the most important element of an asset allocation plan: an investor's split between stocks and inflation-adjusted bonds. To design an asset allocation plan that "slices and dices" the equity portion of one's portfolio between multiple asset allocation classes, other resources are needed.
Below are listed some other useful resources for developing an asset allocation plan. Propsercuity does not confirm or endorse the accuracy or underlying philosophy of these resources. Indeed, the last two resources – both simulators – have the same flaws (backward looking returns and correlations between asset classes) noted in TIP$TER's "Problem section":
Bogleheads forum (dozens of volunteers willing to help you design an asset allocation plan)
A Toy Portfolio Designer by MIT graduate Stephen Rowley (works in Firefox/Safari; does not work in Internet Explorer)
FIRECalc by Bill Sholar (backtests a portfolio made up of selected allocations to 5 different equity asset classes and 3 different bond classes – not including TIPS – with intervals from a 1927-present data set)
Easy Allocator by Nick Cockcroft (backtests historical asset class return data)