Yes, the current FlightFins v2 and MiniFins will work on the Onewheel GT if you attach them to the stock Future Motion Fender. There is a need to drill attachment points and screw them from the inside.
The FlightFin Fender for the XR and the Pint will not work with the Onewheel GT. FlightFins have confirmed that they will design a new FlightFinder for the board as soon as they are released. As the GT is not yet released date is to come.
FlighFins Released their Onewheel GT FlightFender system.
We will design a new FlightFender asap.FlighFins
To mount the FLight FIns to your board you will need to drill and mount them to the stock fender from Future Motion. Here is a guide that explains the process for mounting FlightFins v2 to a stock Fender.
*MiniFins are compatible with all current FlightFenders and boards including XR, Pint X, and GT with FM stock fender. We are currently working on FlightFenders for GT that will be available sometime next year.*FlightFins
Are you uncertain which Fins are right for you, the MiniFins are sleeker giving you more foot space and you can ride bidirectional. The V2 FlighFins will give you a more locked-in feel. For a full breakdown check out V2 FlighFins and MiniFins breakdown.