Hi, Ian,
If that extension actually contacts the sump when the sump is in place, I think I'd like to see more holes for the oil to be drawn in - I can only see 1 hole in the pics. Maybe run this by your Engine Man for his assessment?
Normally, afaik, there is usually at least a 6-8mm space between the oil pump pick-up screen and the sump, so this area (6-8 x circumference of oil pick-up screen mm2) would need to be matched by the total area of any holes in the extension.
I've even run engines without the pick-up screen in place to minimise any restriction at the oil intake to the pump - I wonder how much power it takes to suck oil through such small holes, plus it possibly also adds unwanted heat into the oil. But this was on engines that had an anti-drainback valve in the oil filter, idk if it would be safe on the 500?
Also, if there is any possibility that fitting the sump will try to push the extension up against the spring pressure, you might need to extend the notched cut-out a bit more.
Great workmanship and attention to detail, so far.
Regards,
Al.