Most "long" plugs work well.
I've seen no advantage to the long plugs with idle bars, even when the engine is mounted inverted.
For a comparison:
Caption: From left to right: Stock Evolution 1.00NX 2 Stroke Glow Plug O.S. "F" 4 Stroke Glow Plug Stock SuperTigre .75 2 Stroke Glow Plug O.S. A3 2 Stroke Glow Plug