ppp direct with nat

[george]

I use ppp -direct to allow dial ins but dont want to 
waste my few static ip's i have so is there
a way to make the dialin lines one of the
unrouteable ones and do a "reverse nat"
to my real ip?

I was thinking something like running 
ppp -nat -direct dialin

and using 
(ppp.conf)

dialin
 set ifaddr <myrealip> <the unroutable ip>
 enable proxy

this dont seem to allow packets out of the network though

I need help on this one.


Thanks

george