Thank you for replying!

Yep - searched IRS.gov and http://www.window.state.tx.us/taxinfo/sales/ site and called IRS Before posting the question...
Seller finally called competitors for correct mystery info. Seller was misinterpreting requirements, per their legal and accounting advisers, and requesting multiple docs. Better safe than sorry, for their sake.
Countersink and chlorine are not related. Just got same statement, "in order to maintain warranty" reply from 4 diff retailers with 8 diff answers to two separate questions, 1st - regarding countersunk depth, and 2nd - regarding chemical system.

I have yet to find the actual Dough Boy document stating what countersink depth and what chem syst, if any, will void the warranty. Maybe another mystery or I haven't asked the right people yet.

Thanks again for your time!