Mainly for RF reasons the prototype design 1 is 'reshaped'. 
The two detector boxes are mounted together in a centerframe 
before installation in the vacuumtank. This makes it possibile 
to install WF suppressors along the sides. 
There is one feedthrough flange at one side of the vacuumtank.

Comments:

Plus points:

Center frame much stiffer 		
   	optimally positioned short legs, no more problems of bending
	not any longer 'in our way' (more accessibility to critical 
	items of VD, see below)

All 'referencing' is achieved with a much simpler design
	alignment and reproducibility

VD easier to mount and position in the tank
   	build in complete VD at once
   	solves accessibility problem on one side of the beam pipe
 	no more need of tilting mechanism during VD installation

Easier access to the critical WF suppressor 	
	more accessibility for connection to exit foil

Possibility to install WF suppressors along detector box sides
	required for position 'open' !!

Much space left on one side of the tank  	
	secondary vacuum pumps and, if required,  a titanium 
	evaporator with much more favorable design conditions 
	(comes from side, instead of from front of tank)

Pumping on the detector boxes is more efficient

Minus points:

re-do FEA calculations 

two detector boxes are not interchangeable any longer
  	(but individual stations can be)

all feedthroughs on the same big flange
 	all cables and repeater cards on same side
	present choice of feedthrough limits total number of pins
					to about 25000 !!

Pictures:

Total design		Si detectors
Vacuum Tank	Si detector	Center frame