i don't use FL Studio often, but when i do, i bounce stems out of FL.
i've tried both using FL as a plugin & rewired. it's weird how FL's tempo read-out doesn't even match the tempo of Sonar. but i have experienced massive crashes when trying to integrate FL into Sonar. when i asked for tech support from FL this past year, i was told that they didn't even own Sonar over at Image-Line. that was the last time i bothered trying to use FL Studio inside Sonar