Are any of the shorter Duro-Test lamps Power-Twists? I have a couple of those oddball 4' T9 30/34W Energy-Twist lamps. They seemed to work OK on T12 HPF magnetic ballasts even though the etch suggests they're for T8 or Electronic T12, though they actually used a bit more power than a normal 40W lamp.
I had two shorter power twist lamps, one sold already. I believe one is left.
I have a full case of the standard length (will not separate) as well as several loose ones.