Great show. I went to the Dawn Patrol at WPAFB as well. I still feel horrible for that guys' poor N-28.
It is my understanding that it all has to do with weight. If built to full scale most planes would require a much, much larger engine. In the cases of the Se5's, they would need twice the engine size. Cost, maintainence, and overall headache is a lot less........................ so the pilots where saying.