Thanks all for your reflections on i-orp. I agree that the tax calculation is probably fairly basic, but I think it errs on the conservative side.
The reason I think i-orp is cool is because it lays out a possible future that's "thought about" the big stuff, and has a plan that's optimized (limited, of course, by the level of detail within the model).
I realize that the near-term stuff will need a finer look (TT), but with the general direction that the model's output gives me, I can glean what it was "trying" to do, and head off in that direction.
My validation was to download the result and run a few parallel calculations. Obviously I can't validate that the result is optimal, but it looks like I could execute the recommendations, and it would work (given the limitation that it gives equities exactly X% gains per year, year in, year out). Another useful feature that I didn't mention above would be to have it run the optimization with the defined inflation and growth rates (as usual), but present the output with inflation backed-out. That would make it easier to validate. You can set inflation to 0% and reduce the gains by the inflation rate, but I don't think the optimization would work the same then.
I make a table using Turbo Tax each year to determine how much to spend from the IRA vs Roth's.
Is this calculation basically to tell you how much IRA money to pull in order to snug up against your tax bracket or ACA limit, then pull the rest from Roths?