This probably is the right place- it's just very slow here now, and very few ever bother to look in the fmb section.
I'm not an expert on the C# coding but one thing that strikes me is you are using the SYSTEM readings, have you tried the
instrument reading?
[Inst: Fuel Reserve]
/// <para>Returns fuel level indicator reading.</para>
/// <para>Generic subtype (-1) shows combined reading in all tanks / controlled by selector switch;</para>
/// <para>Other subtypes point to fuel tank number in machine's list.</para>
/// </summary>
I_FuelReserve,
I've not played with fuel levels to work out consumption, but the Instrument values seem to work- with the possible exception of the compass which is reported to be non functional.
If this doesn't help it might be worth asking over at ATAG forums
http://theairtacticalassaultgroup.com/forum/forum.php
which is pretty much the place to go CoD wise these days