DVDR1640P can't write at 2x?

I need to burn my playstation2 backups @ 2x so that it will read them easily. But I could not get my DVDR1640P write at 2x on any kind of media…
(I’ve tried : dvd - R / dvd + R and several brands like TDK, Maxell …)

Does that mean that I’ll never be able to perform a 2x session ?
If that’s so, does the BENQ model has 2x writing capability?
Maybe I can consider cross flashing with the latest Benq firmware?

Thanks in advance.

Try at 4X, that should work fine on your ps2.