hi
i fly a hawker with pro-line 21,great airplane.
you can use the APU in air.
the TKS you use it before enter in ice condition or visible moisture or
temp between -10/+10.
if you want a personal suggestion forget the old 800xp,buy the
hawker 1000 1400lbs more of fuel 3ft longer keeping in the air for more
than 7 hr.the best midsize ever built.