[NLRS] 10GHz feed horn design & question

[W0ZQ at aol.com]

I finally measured the dimensions of my "larger" 10gigs offset dish that I  
have been using this summer.   Here are the stats:
 
Largest axis (top to bottom) = 654.05 mm
Shortest axis (left to right) = 596.90 mm
Deepest spot along largest axis = 58.42 mm
Deepest spot from bottom along axis = 292.10 mm
 
Using hdl_3b3, this dish, at 10368.1 has the following attributes:
Focal length = 357.9 mm
Full parabola f/D = 0.3
Focal point is located 357.92 mm from bottom edge and 611.73 mm from top  edge
Large axis tilt (to get beam on the horizon) = 67.2 degrees
Use a feedhorn design of f/D = 0.68
With 50% efficiency, gain is 33.2 dBi
With 60% efficiency, gain is 34.0 dBi
 
So then I punched the f/D = 0.68 data into the horn design and  generated a 
template for an 11.29 dBi horn (at 10368).   The horn that  is currently on 
this dish is a RCA DSS horn with a gain of 11.49  dBi.   When I hold the two 
templates up against each other over a  strong light source to compare them, they 
are indeed just a little bit  different.
 
So, for the dish guru's out there, will changing the feedhorn from the  
current RCA DSS feed horn (11.49 dBi) to a more appropriate feedhorn (11.29  dBi) 
provide better illumination for the slightly larger dish and hence a bit  more 
gain ?   My thinking is yes, but the improvement may be on the  order of one 
dB or so (its not the difference in the gain of the two  feedhorns ..... is it 
?), certainly not a BIG deal, but a deal none the  less.   
 
73,  Jon
W0ZQ