Has anyone relocated the oil tank to have it lower, and less likely to cause hydraulic lock? There is enough room on the people side of the firewall, where the header tank used to be.

Have other owners with early 912 installations experienced hydraulic lock?

I just went through the hydraulic lock recovery process on my other ultralight. It too has the oil tank bottom at the upper design limit of about equal to the crankshaft / oil pump. Hydraulic lock was never an issue, until I dismantled the plane for ground transport. During disassembly the fuselage was on a slope, which must have been enough to start the syphoning. Not what you would want to happen anywhere else than your home base.

So as I rebuild this model 3, why not add a few more weeks to design and fabricate yet another better way of doing things? <many times I envy the new kit builders>

If the oil tank moves behind the firewall, there will be a huge open cavity over the motor, as I have scrapped the hot air box in favour of heat probes in the carburettors. mmmmm, will that mess with the air cooled cylinders?