5 Gbps USB 3.0 PIPE interface via Cyclone V GT 6 Gbps transceivers?

Can anyone please confirm that it is not possible to configure Cyclone V GT PIPE interface (v15) for 5 Gbps? And, if so, why not since the transceivers support up to 6 gbps? The Megawizard only allows configuration to 2500 Mbps and it compiles okay. When manually editing the IP to 5000 Mbps per below:

altera_xcvr_pipe# (

.device_family ("Cyclone V"),

.lanes (1),

.protocol_version ("Gen 2"),

.base_data_rate ("5000 mbps"),

.pll_type ("CMU"),

.pll_refclk_freq ("100 MHz"),

.deser_factor (16),

.bypass_g3pcs_scrambler_descrambler (1),

.bypass_g3pcs_dcbal (1),

.pipe_run_length_violation_checking (160),

.pipe_low_latency_syncronous_mode (0),

.pipe_elec_idle_infer_enable ("false"),

.mgmt_clk_in_mhz (100)

I'll end up with the below error:

Error: Clock Divider Parameter 'data_rate' is set to an illegal value of '5000.0 Mbps' and PMA Direct parameter is set to 'false'. If PMA Direct is false, the value is illegal for protocol mode: 'pipe_g2' with a device speed grade of '7_H5', PMA WIDTH of 'ten_bit' and byte serializer mode : 'en_bs_by_2' and latency 'dis_pcs_bypass' on atom 'Pipe0:pipe0_inst_USB_A|altera_xcvr_pipe:pipe0_inst|av_xcvr_pipe_nr:pipe_nr_inst|av_xcvr_pipe_native:transceiver_core|av_xcvr_native:inst_av_xcvr_native|av_pma:inst_av_pma|av_tx_pma:av_tx_pma|av_tx_pma_ch:tx_pma_insts[0].av_tx_pma_ch_inst|tx_pma_ch.tx_cgb'. If PMA Direct is true, the value is illegal for PMA-PLD WIDTH of '10'.

Is there any way to tweak things so I can get the PIPE interface to support 5 Gbps (actually USB 3.0) or would I have to drop down to a lower interface (like Native PHY)?

Thanks.