Disable NAT on MR814v2 & PPTP

hi,

i recently purchased a MR814v2 wireless router. unfortunately i am not
able to disable NAT on this router (and netgear-support isn't that
helpful either).

my setup is as follows:

i connect to my ISP via PPTP and one IP address gets assigned to the
WAN (PPTP) interface via PPP. Another network is routed to this IP by
my ISP. (exactly this setup worked fine with my zyxel non-wireless
router).

because several IPs are routed to my account i don't need NAT. netgear
support advised to disable DHCP on the netgear to disable NAT, but if
i do so my connections still get NATed.

is this setup (PPTP without NAT) possible with the MR814v2?

also does someone know if the MR814v2 firmware supports "weak iv
filtering"?

cu
/gst