George,
Electric screwdrivers are wonderful things.  Obviously you can't pull
the upper plugs or perform other work on the top side of the engine
without removing the plenum top.  The large number of screws was
pre-determined by the existing hole pattern that once held all the
silicone baffle material.  
<<more difficult to inspect or work on the engine ???>>
Relative to my previous set-up I am about even; more difficult up top,
easier on the bottom.  Prior to the fully enclosed plenum, I had molded
FG parts installed just inside the lower half of the inlets in an
attempt to prevent the airflow from separating (was only marginally
successful).  These pieces had to be removed every time I wanted to
remove the lower cowl.  I was glad to get rid of this hassle and accept
the extra screws for the plenum top.  I find the extra minutes to gain
full access to the engine to be well worth it, given the immense cooling
improvements.  I was fortunate to be able to test the system with 100+
deg F OATs and had to pinch myself when I observed the new cylinder head
temperatures during take-off.  Every phase of flight is improved from
taxi, take-off, climb to cruise.    Even the oil cooler located infront
of cyl. #2 benefitted.  Previously, flow separation, which the parts
mentioned above attempted to correct, off the lower edge of the inlet
was blanking the cooler and it would not cool while flying below 120
KIAS regardless of power setting.  Now it cools all the way down to
something less than flying speed.
It would be nice to quantify all the positive and detrimental
contributing factors in any given cooling system.  Perhaps you have been
able to do this and I too am interested in attending your baffle session
to hear about your experience in this area.   I was stuck having  to
make qualitative judgement calls during the design and construction of
this system, but I really like the results.
regards,
Chris



Christopher Zavatson
Mobility Technologies
United Defense
(408)289-4329