re:reflection coefficientsof magic tee

hii..
im simulating a planar magic tee.for minimum reflection at a particular frequency we can use iris.
can u tell me what will be effect if i change iris length and position of iris?
due to change in position of iris ,the reflection coefficient parameter changes(minimum of maximum) and
due to change in iris length ,the return los shifts to left or right.
is that true?

Waveguide transmission systems are not always perfectly impedance matched to their load devices. The standing waves that result from a mismatch cause a power loss, a reduction in power-handling capability, and an increase in frequency sensitivity. Impedance-changing devices are therefore placed in the waveguide to match the waveguide to the load. These devices are placed near the source of the standing waves! irises, are used to introduce inductance or capacitance into a waveguide for matching..... as far as i know changing position and length will cause effect that you stated... I am not though 100 % sure about it