Well it has arrived, undamaged despite having travelled about half way round the world since leaving Perth Western Australia.

Checking the wooden bits first:
The neck looks to be OK, probably will need a fret levelling when completed and a tweak on the truss rod, but that is to be expected as even new Fenders and Gibsons need that all too often.
Body looks OK, but that is going to get a lot of tender loving care from various tools so any minor imperfections will vanish in a cloud of sanding/saw dust.
Neck/body joint is over tight, with the neck about 0.5mm wider than the pocket (it's a screwed on neck). Easy to solve and better that way round than the 4mm of packing on width that was needed on a friend's bass (not from PBG). Not able to comment about alignment yet as I've not got the tools and sandpaper out yet.

Now for the first question....
How does one go about fitting the bridge/tremolo unit (from Overlord of Music) . There are four mounting holes in the base plate, but they are hidden under the moving part, which "anchored" by spring pressure against two posts. The spring is held in a cavity between the two lumps, pressing firmly against a stop on the fixed part and the adjuster screw on the other. It's a heavy looking spring, and I fear that releasing the tension might send it, or something else into either orbit or that dark forbidding corner where lost screws lurk unseen. I foresee bloodshed (mine) and that is a long way down the list of desirable outcomes.