I would definitely either go at a different time or take a different route. If you have the time the TA or the NT would be better choices that time of year. If you need a shorter route there are lots of other great tours. How about the Pacific coast for example.
BTW: Where I wonder about Mr. Bent's comments is where he says, "You could do a modified Northern Tier with about the same mileage". Is that true? Glancing at the map it doesn't look possible to shorten the NT by all that much. The ST is over a thousand miles shorter after all.
I don't see how it is likely that an NT could be done in nearly as short a time as an ST could.