me. What should I be inspecting, just to make sure that its up
to the
job?

Nothing.

A badly DESIGNED but wonderfully constructed raft will slowly
sink or drift off down the garden.

A well designed one, which will incorporate a certain margin of
error in the calcs, will probably stand some slightly off
construction under a conservatory which is a lightweight thing.

You aren't in a position to check the cals, so... Close the
curtains. Pour yourself a drink. Relax. Stay away until it is
done.

W.