colspec elements always go before the first thead or tbody (= group of rows) of a tgroup (= group of groups of rows). Please take the time to learn the table model of DocBook[*], you'll save yourself a lot of time and frustration.
--- [*] There are just 2 table models in the world: XHTML and DocBook (AKA CALS). Therefore this is not such a big deal. This email and any files contained therein is confidential and may contain privileged information. If you are not the named addressee(s) or you have otherwise received this in error, you should not distribute or copy this e-mail or use any of its content for any purpose. Please notify the sender immediately by e-mail if you have received this e-mail in error and delete it from your system
