Hi -- I just noticed that for that single country in the world
still using medieval-age units, my last formula can be used quite nice
(I think  :-)  ):

Measure the four longest tubes (2 on the left, 2 on the right) and the
four shortest tubes (all in the middle, probably) and add up their
lengths in _inches_. Add 10% - then the result is the number of _feet_
needed for the complete tracker bar tubing.

Example (invented by random variation of 10 and 24):

   24+23+24+24 + 10+10+11+11 = 137
   +10% = +14
   Sum  = 151

Notice that the 10% is _not_ a "safety net", but is part of the
algorithm.  If you need more safety, add 15% or 20% ...

Regards
Harald M. Mueller