I've never tried floating this stretch, however my NJ canoeing bible "Garden State Canoeing" by Edward Gertler says the following:
This section is most often canoeable in late fall, winter and spring, however it can stay up for 3-4 days after a hard rain and 7-10 if the weather has been wet.
It also says that for the stream to be navigable, the gauge at Rt 46 in Columbia should least 1.3 ft, the gauge in Blairstown should read 2.2 feet minimum and the gauge at Flatbrookville should be at least 2.5 feet. Also check out this site for potential put ins and take outs
https://paddling.com/paddle/locations/
Good luck and let us know how it worked out
