Here is the picture of the N-Gear Jumpstop on a Calfee. Notice that the metal top part is bent so that the derailleur clears it. The seat tube starts to expand just below the Jumpstop band. I don't think a Dog Fang could get low enough for a 26 toth chainring since it appears to be at the same height as the band.
Which dia Jump Stop did you use?
I assume it is directly on the tube and not on the FG sleeve.