Thanks for your suggestions.
Mr. Rooney, these will be verticals on ETFs, equities and indices, no futures. Any place else I can go to get bid/asks on those?
I've been doing vertical credit spreads for years, but these were EXISTING spreads found on ToS Spread Hacker, not newly created spreads.
Stepandfetchit, of course it will be a limit order.
Tommcginnis, been there, done those (not the $1,000 tutor!). Recall please that I posted that "I have not found anything on this subject in the literature."