Hybrid OFDM-digital filter multiple access (OFDM-DFMA) PONs exploit software configurable digital shaping filters in ONUs to multiplex multiple gapless OFDM channels at different radio frequencies and utilize a single FFT operation-based pipelined DSP procedure in the OLT to simultaneously de-multiplex/demodulate all OFDM signals from various ONUs without requiring any digital matching filters. In this paper, aggregated raw 30Gbit/s over 25km multipoint-to-point upstream signal transmissions of IMDD OFDM-DFMA PONs are experimentally demonstrated for the first time. Experimental results show that a reduction in ONU-embedded digital filter length from 256 to 16 just decreases the receiver sensitivity by <1dB, which are independent of ONU spectral locations. By utilizing a digital filter length as short as L=16, fibre transmission impairments (channel interference) are shown to give <1dB (<2.5dB) receiver sensitivity degradations. In addition, a >3.5dB (>5.5dB) ONU launch power dynamic range is also achievable for an aggregated upstream transmission raw capacity of 28.12Gbit/s (23.43Gbit/s).