Here's something else to consider.  I just learned an interesting fact about
the 912.  It has a dry sump system, and it's oil cooler is on the "suction"
side of the oil pump.  It wouldn't be impossible to set up a 13B this way,
which is something else to consider, but then you'd have to worry about
sucking the cooler flat, rather than over pressurizing it.  Might be safer
to suck air, than spew oil though.  Bottom line is that I'm hoping we can agree that oil coolers need special
consideration when it comes to durability.  The evap core seems to be OK for
water, though I'd like to stop using them for that as well.  I suspect there
are strong pressure pulses from the oil pump that are fatiguing the cores.
For the record, this isn't just a problem with the evap cores, because we've
had a Setrab fail, as well as whatever was being used in the Velocity
(twice).  Installation is important, but it's also hard to deny that Mazda
built their coolers extra tough for a reason. Rusty (trying to catch up)