Yep, weight and making sure the rear truck has the right balance and freely pivots was key in getting mine running better. I've found that weight helps 98% of the diesels, a vast majority of them don't have sufficient weight. The Aerotrain just has other liabilities that have to be addressed as well as the light weight.
I'm sure you remember my picture of my Lionel Amtrak HHP-8, the difference after adding the extra pound plus of weight had to be seen to be believed. It went from struggling to pull four SuperLiners to pulling ten of them with no problem! I marveled at the difference at the time, I really didn't believe that much improvement could be obtained!
