Bert Modderman Engineer
Here is a description of a 9 dBd double quad and its calculations
L = 0,6 lambda -> this should be considered a minimal length and can be longer.
If you bought a bend one like me, be extremely careful to straighten it.
13 cm example
L = 8 cm
23 cm example
L = 16 cm
There are many ways to connect the semirigid to the reflector. If the reflector is copper it could be soldered.
Good luck building!