Ettins weigh just under a ton.

 

I was re-reading the Referee book from the old Lamentations of the Flame Princess boxed set. It's really good stuff and the PDF version is available for free. James includes a chart in this book for eyeballing the stats of normal animals based upon their weight.

James notes that herbivore would do half the damage listed above.

This time reading that section reminded me of another weight-related D&D items, the article "How Heavy is My Giant?", which I read in Best of The Dragon, volume 1. It includes this handy chart of average weights for human-types of various sizes:

Since people are animals two, we can put these items together and get the totally unofficial LotFP hit dice and damage for big gronkos, like so:

The results are lower powered than the Monster Manual version, which makes sense given the deliberate flattening of the power curve in LotFP. Note that the clay, stone, and iron golem weights are based upon the density of their respective substances, rather than ordinary flesh. Also, all the weights assume that everyone on the chart has the same general build and proportions as an average human. Of course, back in the day when everyone used human minis is various scales for their giant figures, this made perfect sense.