Yes length is a factor then but ONLY in regards to phasing or in some cases impedance transformation.

Yes it does. It becomes 25 ohms. This is the reason that you either use stubs to transform each element impedance to 100 ohms or you use a proper RF power splitter which is actually a tuned piece of feedline that transforms the 50 ohms to 25 ohms. This is called a conjugate match. My pair of 50 ohm 13B2 yagis for 2m will be combined/split thru a home made power splitter/combiner that has a characteristic impedance of about 35 ohms. When placed in at the junction of the two yagis it presents an impedance of 50 ohms to the main feedline. The result is that each antenna is tuned perfectly to 50 ohms on it`s own and the combination still presents a perfect 50 ohm match to the main feedline.

You are starting to confuse me.

The questions you ask would lead me to believe that you in fact know more than you are letting on. Talking about making Q-sections and phasing lines etc yet you don`t know about common mode currents?

Hmmmmmm.............

Hopefully I don't have to use this