I was unable to find the article mentioned in the VAF archives, but this is close
http://rvbuildershotline.com/articles/grossweights.html While it does not say anything specific, it does make some obvious points.
" Several respondents stated that they had calculated G-load strength of their airplanes based on a ratio of standard category weight relative to aerobatic gross weight to arrive a higher gross weight.
For primary structural considerations, this is basically valid, but it does not take into consideration possibly safety issues related to higher stall speed, landing gear loads etc. Just because the wing won't break because of the higher gross weight doesn't mean that other bad things can't happen. "
Out of curiosity, what did Vans say to make you raise the gross to 1600?