Hi Phil,
Having done this before, all I did was use a pair of pliers to gently bend the tab (using a vice or clamp to ensure just the tab got bent) at the top end of the rail, then sliding it on. Your recent photo shows them correctly fitted on the outside of the bow, not the inside between the pulleys.
The tab only needs bending by about 45% to give you space to wriggle the slider into position, it can then be gently bent back into place. Slight heating to the metal might aid the bending, but I wouldn't heat the plastic as it might have nasty side effects.
Hope that helps.
Ian

Having done this before, it just took a bit of bending. I had another lock pliers few inches from the top and use another pliers to pry it out a bit. Doesn't require a lot of force at all, I don't think you even need to use the vise.



