[TowerTalk] Reflector element question...

[Geoffrey Way]

I'm converting an old Moseley CL-33 tribander into a 6m beam.
It has a 12 foot boom, so I'm following the suggested layout in the
ARRL antenna book for a 5-element design shown on p. 18-27 of
the 2007 (21st) edition.

My question is, if I have some extra length on the reflector element,
would I get any additional front to back ratio if it were longer? And,
is there a length that becomes too long, having some adverse effect?
Or is it just a case of no further benefit? Perhaps some other effect
that I am unaware of?
-- 

             Geoff Way, KA1IOR