acrylic vacuum chamber

Hi, to maintain a 1 kelvin environment, one needs to isolate the
experiment with a vaccum. Not doing so would require way to much liquid
helium to attain that temperature. These chambers are usualy made of
stainless stell. However, I am considering using cheaper acrylic for
the chamber. Anyone knows how easy it is to maintain a high vacuum with
an acrylic system? I am also hoping to create an easily openable door
to manualy modify the various components that will be put inside (not
under vacuum obviously). How should I build such a door with acrylic
that can provide a seal of up to 10^-8 torr.

There is also a second problem called outgassing. Under high vacuum,
materials will evaporate a very small number of their molecules into
the air. For aluminium that number contributes to 10^-9 torr, so 10^-10
is not reachable with an aluminium system. What torr limit does acrylic