Turns out that there are so many minute adjustments needed to the multitude of cable and tubing routing, that the individual avionics instruments in the front panel have to be put in one-by-one. As the wires compress behind the units, they take on new shapes necessary for routing, chafe protection, etc., and those new routes affect the layout of the pitot static plumbing as well. Earlier I had thought I would try to make the pitot static plumbing long enough that the units could be pulled out while still attached. However, there's no longer any point in doing so -- if there ever was. Unless the entire panel can be efficiently (?) slid into and out of the center panel space as one unit, the individual units are placed one-by-one anyway. In fact, all four of the major instruments (EFIS's, audio panel and A/P) attach to the back of the finish overlay panel anyway... or to put it another way, the finish panel attaches to the front of them. Unfortunately, if the whole panel will not lift out as a unit, maintenance will require gettting underneath -- which will be tough to do with a fixed control column installation. Perhaps there's a way to re-engineer that. In the meantime, the center instruments are going into place. With all the wiring behind, they're not quite as precarious as they look in this photo.

The thornier issue has been tracking down pesky leaks in the pitot plumbing. Initially, there was an airspeed leakdown at the rate of about 1/2 knot per second! When "none" is the standard, that's definitely too much. After isolating sections all along the "common manifold" of the pitot plumbing, I determined that most if not all of the leakage is occurring at the 1/8"  pipe thread junction between male Nylo-Seal fittings and female brass fittings on the instruments. After taking steps to seal those better, the leakdown rate is now 0.13 kts./second. Still too high, but a lot  better. With a little more attention, I should be able to lock this down properly.