David Carment is giving his four a Porsche-like secondary oil cooler and 
wonders what to do about dipstick oil levels.  I would say that you definite-
ly do want to add extra oil, to maintain the crankcase oil level at stock.
Otherwise you'll risk oil starvation during long fast turns.  (I would also
recommend an oil temp gauge, as a check on the efficiency and integrity of all
the new stuff you're adding.)  You can calculate (or just measure) the added
volume of the lines and cooler, put in that much add'l oil, and make yourself
a new line on the dipstick.  Double-check by checking the level immediately
after shutdown; it should take some time for the extra to return to the 
crankcase, so over a period (minutes? hours?) after shutdown, you should see
the level go from the stock full line to your new higher full line.

FYI Porsche sixes take a completely different approach to oil-level checking;
you check with the engine warm and running.  The dipstick is in the oil tank,
where oil isn't getting thrown around the way it is in the crankcase.  Years
ago I saw an article about dry-sumping a Type 4 engine.  It struck me as the
wrong way 'round to solve the problem, when the Porsche six fits so nicely.

B.