O.K. here we go ,the main reason for changing the rear arm on a PROFLEX XP-X FRAME is that if the two pivot axle (left and right )are not done up tight enough ,the pivot axles will move ,making the counter bores in the frame out of round ,as in the second set of pics, (not too clear )http://imageshack.us/a/img515/5678/proflex2006.jpghttp://imageshack.us/a/img197/3097/photo0272au.jpg
This is shown in the black marks on the frame ,plus the axle pivot will move around in the counter bore in the frame and not a firm fit .
The nexst two pics are the original parts ,there will be marks on all mating faces (frame and pivot)http://imageshack.us/a/img89/700/proflex2003.jpghttp://imageshack.us/a/img521/2856/proflex2002.jpg
One answer i think is to make two new pivot axles and use two needle roller bearings ( 4900 2rs, 22mm od X 14mmID X 13mm long ,£9-£20 each )
the next pics are of all thats needed !http://imageshack.us/a/img32/6578/proflex2004.jpg
and yes i am lucky enough to have a small lathe and mill at home .
If any body would like more info ,or drawings let me know.
I think i have rambled on too much and need a rest