This is turning into quite the authoritative thread on all things SMS forwarding :-) Another app I hear about in this connection is DeskSMS (Miketg11 mentions it as being $ 4.99 / year). Maybe have a go at that too - hopefully there is a free trial period?
PhoneLeash feature updates are still in the "In" tray. I took the time instead to update the website
some, it was hopelessly out of date. Who knew making a little app (and free!) would mean so many late nights!