At Nationals in 2008, the B division tower rules were almost identical to the current B rules except for the scoring formula. The top tower had a mass of 4.3 g, held 13.700 Kg, had an efficiency of 3186, and under the new scoring would have a score of 43.649 million grams. The second place tower had a mass of 4.82 g, held 15.000 Kg, had an efficiency of 3112, and this year would have a score of 46.680 million grams. The third place tower had a mass of 5.18 g, held 14.560 Kg, had an efficiency of 2811, and this year would have a score of 40.925 million grams. Efficiencies dropped considerably after these. These were remarkably good towers and the rules aren't much different, so I think that scores above 50 million grams will be rare.
I can't find my scores for Nationals in 2006. If I come across them, I post the top ones; maybe someone else on this board can find a copy. The new C division rules are virtually the same as that year, except for the scoring, so I suspect scores derived from 2006 results will be a decent guide to expectations for this year.
Really, the only differences are that wood of any cross section may now be used, the rule prohibiting touching of the chain against the tower during loading was omitted, and the rule prohibiting sagging of the tower into the opening during loading was omitted (these are only prohibited as initial conditions, I have no idea why those rules were dropped). It would take a dramatic breakthrough to get scores around 60 million grams.
Grand Haven, MI