jay,
you should be able to set it up that way. my external 21" lcd is where i keep my main plan workspace.
i imagine your sager has an ati video card, mine is a nvidia, so i do not know exactly how to set yours up. i have many options available in the advanced settings, n view where i select 'dualview'. also you can only move app to 2nd monitor when it is minimised. or using the n view option that adds a toolbar to top of window. see if there is a "hydrovision" setting, i think that is ati's n view tool for setting up multiple monitors.
http://www.ati.com/companyinfo/glossary/hydravision/features.html
also, i do not run my main ac8 window maxed, i adjust it to line up w/ the right side of the info bar. that way i can run the bar up to the top of the screen.
just experiment for a while, you will get it. once all set up save before you close and it should open up the same.
tim hanagan
aaha! design studio durango, co
27" retina 5k iMac 4ghz i7 os 10.13.6 m395x 4 mb, 32gb ram, 512 gb ssd ac 22 current
15" retina mbp 2.6ghz 1mb 16gb ac 22 current[/size]