Word of caution, when I tried a Richardson breach bar in my 505, it didn't fit. The bit that goes over the metal loop bit in the trailer was at too tight an angle, I couldn't even 'make' it fit. Whether an Ifor will fit a Richardson or not, I don't know.
Of course, it could have been an age thing too, the Richardson was pretty old, so design might have changed now.
I have a pair ifor 505 for sale they in my shed as ive bought the bigger ifor they are burgundy they do have the ends that expand to fit other trailers !! pm if interested.
wen i bout a trailer from wittersham trailers they made me a full length one for my trailer because i needed to travel my mare without the partition. try giving them a ring x