Robert,
  I'd be very suspicious of the dual LSE power loss claim.  I wonder if that engine builder had them timed properly.
I know Performance Aero Engines will deliver a rebuilt Cont IO-550 or Lyc IO-540 with dual LSEs installed and with all of their other performance mods, they're getting a whopping 370 h.p. out of normally aspirated engines.
  I have one Lightspeed and one Bendix mag on my plane and I can state unequivocally that if I run on one or the other, I go faster (and the engine runs much smoother) on just the Lightspeed than just the mag.
  Skip Slater