Tractor and maximum FFT size

I’m using tractor with a QA401,
I have some high distortion plots that for some reason give lots of ripple and ringing when doing frequency response with the standard 32K FFT size. If I jump up to 128K FFT the problem mostly goes away.
I can make this work in the QA401 app and make a mask no problem.

However it appears that tractor does not support a FFT size above 64K. Is this correct? Why can I not put 128K FFT into tractor without getting an error?