Has anyone come across or developed a decent fuel planner for this bird by chance?

SimBrief has a Citation II profile and it seems to be pretty good.  If you're a member (free) of FlightAware.com, they have a flight planner for the United States that also includes a Citation II profile and will give you a pretty accurate fuel loading as well.

Yeah.. I noticed they had a profile for the C550 in their database, but for some reason the weights can't be updated to reflect the Carenado bird. It's 'close enough', though, so it'll work for me.

Excellent RW fuel burn rates can also be found at fltplan.com . When you create a flight plan using the S550 as your aircraft the navlogs will display your estimated fuel burn based on current RW winds aloft - cruise altitudes - ISA, etc. Good stuff