I agree whole heartedly mate the pinion needs to be a one piece shaft with a double taper roller bearing, as every schematic of a trans axle i can find has, with the pre load taken by a nut on the back end.
unfortunately your right there too mate its a no win situation,, I'm personally down the drain not only for the money I've poured into it to get it to this stage, but i also took a sizeable hit on the sale price of the macca as the trans was an unknown quantity, and i know for certain the owner isnt going to spend any more money on it, so its pretty much come to a dead end i'm sad to say, from this end anyway. whether Leon wants to continue refining it or not i have no idea.
so the plan moving foward is to source another trans, i do have a lead on an LG500 MK2, also Fran has a box that would do the job, so at the moment were waying up options.
cheers John