Firewall - Where do you put everything?

How in the heck am I going to get everything on that little bit of firewall?  

A nice CLEAN Firewall with nothing to clutter up the smooth clean surface.  Now the fun begins.
First things first.  The FADEC system electronic spark controls are required to be placed within a certain area on
either side of the center line.  Problem number one, the engine mount covered almost every possible location for
the sending units.  The black rings around the pads on the engine mount are temporary 1" spacers needed to move
the engine mount forward one inch.  This not only opened up just enough space to mount the sending units, it will
give needed space for the rear of the engine and accessories.
Nothing really mounted yet but its already starting to look like a lot of fun.  The power ground and the brake fluid
reservoir have been added in the most out of the way positions I could find.  Drilling holes through that Stainless
is sure fun and can destroy a drill bit in no time at all.
Is it an art...or a science?  Trying to locate everything on the firewall to give both access and safety for routing
controls, fuel lines and oil lines is more of a trial and error than art or science.  I picked the lowest and closest
point for the GasColator.  The ugly black marks show the plan for routing the fuel line.  This position will give me
a fairly straight shot to the engine fuel pump shown in the upper left.  A flexible hose will be used with a tie off
to the engine mount.  The remote oil filter is also in an easily accessed position just below the engine adaptor.
Finding a good position for the oil cooler that would allow for good routing of the scat tube supplying the cooling
air was also a trial and error experiment.  I hope this position will work out OK and be clear of all the exhaust
pipes when the oil lines are installed.  The plan is to use right angle fitting that will direct the oil lines directly upward.
The stainless steel firewall has been removed to show the fiberfax facing.  The main reason I included this was to
show the forward mounting of the protective pan under the fuselage to protect it from the heat of the exhaust
system.  I still have about a dozen more holes to make in the firewall for control cables, battery cable, and electrical
cables.
Before putting the stainless steel firewall back in place I used a random orbital sander to remove the shine from the
surface.  I like this surface treatment instead of the mirror surface that shows every scratch and finger print.  One
thing to note is the three large opening.  The top opening is for a "T" fitting that will supply heat for the windscreen
defroster.  The other two openings will be used for the heater control boxes.  (One shown in place.)  The placement
of these openings was picked to minimize the amount of scat tubing that would be required on both the inside and
outside of the firewall.  The heater shroud will be on the co-pilot side.  The heater output will be split by a "Y" tube
to the upper defroster input.  The second tube will be split to the two heater controls using another "Y" tube.  This
gives the pilot and copilot separate heater inputs.  The inputs are directly behind the rudder pedals and will have
a hood to direct the heated air downward and under the rudder pedal platform.  When the heater controls are closed
the heat will be directed down toward the cowling air exit.
The inside of the firewall is going to be equally crowded but with slightly different issues.  The inside will be very
crowed with wiring and other fixtures.  This shows the inside mounting of the common ground connection.  The
bracket shown in this photo is part of the support system for the instrument panel.  The entire instrument panel
will be shock mounted.  The bracket shown connects at two points on the top of the instrument panel.
And I still have another dozen holes to put into the firewall before it is complete.  It already looks like the target
for machine gun practice and there is not a single hole that is not required.