Yes, Bernie, I've made progress, mostly measurements of temperature and pressure in a variety of locations. Recall I don't have the slightest issue with CHT. I really want a little less cylinder cooling and a bit more oil cooling.
Here's the rub...my system is not like yours, so the following may not apply well for you.
I'm running low velocity inlets and a throttled exit with a more-or-less sealed lower cowl. The lower cowl volume runs almost 7" H20 higher than a measurement point just aft of the cowl exit, with the medium exit panel, not the small one. With this cowl system I cannot dump the oil cooler into the lower cowl volume per conventional methods. It must be ducted to the cowl exit.
The exit end of the oil cooler duct system is several inches inside the cowl exit (ie forward of the firewall - see post #50). Pressure measurements tell me that location is roughly 3" H20 higher than the aft-of-cowl-exit location. Thus the simple way to increase mass flow through the oil cooler is to extend the oil cooler duct exit point rearward to the firewall plane and tap the lower pressure.
Another way would be to improve the oil cooler exit duct shape. Right now I think it chokes flow because of the shape of the fiberglass transitions and because of the SCEET hose bent into a 90; the interior wall is hardly smooth. I intend to build a new all-glass duct with a far better shape, with some improvements at the point where it dumps at the exit. Initially I will not extend it rearward. If I can get enough mass flow with duct shape improvement I will still be able to throttle cooler flow with cowl exit area reduction. That will be desirable in winter. At the moment I vary exit size with swappable exit panels. Later it may become a variable exit with cockpit control.
Right now temperatures are 95F to 105F on the ramp at midday in south Alabama, with 4000 ft OAT's of 75 or more. As a temporary measure I've taken my mid-sized exit panel and cut a 4" half-moon scallop out of the trailing edge. That moves the low pressure area at the cowl exit forward, meaning lower pressure at the oil cooler duct end. Because of the aluminum exit bell it doesn't change cylinder air exit area very much. A test climb yesterday at gross from 200 MSL to 6500, at 105 knots IAS and full power, gave me a highest CHT of 355F and oil temp of 205F. Oil temp dropped of course as soon as I leveled and allowed airspeed to increase. Quick fix; I may or may not get the new duct done before OSH.
Like your tuft test video...I should do it at some point.
BTW, a probe on the oil cooler duct inlet (a 4" opening on the rear baffle wall) provided the most surprising (to me anyway) temperature measurement; 15 to 18F higher than OAT. One obvious conclusion; all our baffle mounted or ducted-from-the-baffle coolers start with an inlet air temp disadvantage. A dedicated external oil cooler inlet is like a big drop in OAT.