I guess it should be better to achieve something on low level at first. For example there is rfft object, but you can use it only as display for now, you can't get data from it.
Also from pd fft~ help:
The real FFT outputs N/2+1 real parts and N/2-1 imaginary parts. The other outputs are zero. At DC and at the Nyquist there is no imaginary part, but the second through Nth output is as a real and imaginary pair, which can be thought of as the cosine and sin component strengths.
So for pvoc stuff there should be rfft~ and rifft~ equivalents available.