I guess I considered it a stupid question due to the matter of fact debate on flying above or below 400 feet. It made me think that I was either missing something or the only one who didn't know how to easily identify the 400 foot ceiling.

Excellent point on requiring a spotter as your "altimeter." One way around this would be to program an audible alarm associated with let's say 380 feet, this would then allow the pilot to make maneuvers to prevent breaking the 400 foot mark. I might consider this on larger models I intend to build/fly in the future, but I'm not sure I'd be willing to add this type of telemetry to smaller say 40 size planes.

Does anybody have an easier solution?