Ary, Thanks for the input - the plywood and nail method is intriguing! My main concern was the possible differential swelling and contraction of the mud and wood - cracking. Plywood might be more stable and a hollow column will have less material to expand than a solid pole, so this is a valuable piece of info.

However, there is one twist to our APC circumstance: we have built our foundation, having fastidiously faced our urbanite in mortared natural stone, without first setting the posts or post footings. So now, I should rephrase my initial question:

Does anyone have experience building solid cob columns? Any info on strength, seismic or otherwise? Ary, feel free to provide another golden nugget.

Thanks!