Hmm, I'm not sure if I know the answer but I know a man who does - I'll ask on Monday. However, sounds like your standard parallels are close together relative to the extreme aerodromes (from an old text book, limit the projection to: 4/6 of the latitude range between std parallels and max 1/6 of the range above and below std parallels. Distance scale 1.0 at std pars, 1.01 at 1/6 above and below and 0.99 at mid lat).