Need help with Rotax 912 radiator installation!

The title pretty much says it all.

My good friend and neighbor, Leo, is having some cooling problems
on his Zodiac.

The first taxi tests proved the airplane handles well on the ground,
accellerates like a banshee, but the coolant and CHT temps peg in
only a few minutes.

The radiator is mounted near the firewall with an enclosure around it
to direct cooling air through the rad.

The inlets are NACA vents on the side of the cowl, 4" Scat tube to the
radiator enclosure, and a lip on the bottom at the exit from the
radiator.

We tufted the cowl, with special emphisis around the inlets and exit.
The results are about as expected.

The inlet tufts do (eventually) go down the Scat tubes, but there is
a noticible amount of 'bulge' in the strings along the ramp.
One that overlapped past the back edge of the inlet simply stuck to
the surface of the cowling (Man, I hate when that happens!)

The outlet tufts do show a little bit of down angle coming out of
the radiator enclosure. But it's pretty mild, with hardly any
turbulence behind the lip.

We also plumbed up a spare altimeter to several places - inside the
cowl about 1/2 way up the firewall, about 1/2 way down the Scat tube,
in front of the radiator lip, and one behind the lip.

The numbers show the correct pressure differences where they ought
to be, but the total difference was only 10 or 15 feet of altitude.
That's not much pressure differential!

We are going to let her cool off and try clamping an extension to
the exit lip for the next performance. See if that will make any
difference.

If any of you guys have been down this path with a 912 installation,
would you mind sharing what you did, How yours works and how its
built?

Could really use some help figgering thisone out...


Thanks

Richard