Use a longer flat port (5505.45/58 - Macro)

Can i use a longer flat port then Ikelite advise for a lens? This is the case; use a 5505.58 flat port (5.1"-6.1") for the Canon 100mm USM macro and not the 5505.45 flat port (4.5"-5.5"). It is only 0.6" longer so i would say no problem, or am i wrong?

Gr. Mike.

Should not be a problem as long as the port doesn't cut off the corners of your shots

Karl

Just as a was thinking and because of the 'narrow beam' this looks not to be the problem.