re: I do
Thanks for the link.
Al Cameron notes that there are numerous parameters still to test by computer simulations. He has not yet explored all the possibilities of the ratio of the mass of the growing Earth to that of the impactor, or the total range in angular momentum of the system. Jay Melosh (University of Arizona) points out that the physical properties (called the equation of state) he, Cameron, and others use in impact simulations is far from perfect and might lead to unrealistic results. Cameron agreed, noting that he "considers this game very primitive so far."
(italics added)
That last quote sums it up. Modeling impacts is like modeling climate change - you tend to make too many assumptions and have a desired outcome.
We'll get to the bottom of it eventually and gather enough evidence to support something more than speculation or mere educated guesses. Probably 20 to 30 years or so-- 50 years on the outside.
;-)