I decided to see how well a dual monitor setup with a Hercules graphics card would work in my Tandy 1000 TX. I am glad to say all worked well with no surprises. Setting motherboard dip switch 1 on will make the onboard TGA the primary and setting it off will make the Hercules card the primary video. Switching between the video cards using mode co80 or mode mono works as expected. I like this solution better than installing a VGA card and turning off the onboard TGA video completely.