That makes sense to me, too. It'd be an easy test. With so little volume of wort in the heating chamber, I'm sure any lag in the power on/off cycle could pretty quickly heat everything.
I think we have some 1-1.5" adapters sitting around - I'll give it a try when I get a chance. A larger tube would actually be pretty nice, since I could use the ultra low density element I have (it's a 1" element, but it's bent 180 degrees, so it doesn't fit in a 1" tube).