RE: 400 feet
PilotFighter,
Which field in Houston? If you don't want to say, I understand. If you up northwest around Hooks, they do not have their own radar. They get their radar support from IAH.
I assume there have been no complaints. Take a practical approach. Do you get full scale traffic in the area? Are you regularly in their pattern? Maybe a spotter is appropriate.
Good luck,
Bedford