Ken Moiarty posted for all of us...
I don't top post - see either inline or at bottom.

Yes, the window is wide enough for the unit to sit in normal position. And
yes, I already expected to block the top with plywood. What I am wondering
about is how to best go about _securing_ the unit so it cannot succumb to
the force of gravity (which is actually "torque" in this instance, since
this is a rather weighty piece of equipment to have protruding almost
completely to one side of it's pivot line, the window sill). How about
making and attaching a bracket of some kind to the bottom of the unit,
shaped such that it will fit into the 'groove' of the window frame, thus
providing locking support at the base of the unit? And if so, are there no
such items (or kits) on the market ready made for use in slider/casement
windows for just this purpose? And how might I achieve the same at the top
of the unit (where it will meet the plyboard)? [Note, I'm asking these
questions not because I'm not creative enough to develop my own answers to
them, but because I'm looking for the simplest to install and later
uninstall (whilst being safe); given that this is to be only a _temporary_
setup.] Thanks.

Ken



Hehehehe, just too much material here to work with...
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Tekkie