Was wondering what a saddle expert is.. I’ve replaced a couple of broken rails. The only way I could get them back in was to file into the front locating area a little to help them pop back in and create leverage space + a lever locator, then use the right kind of lever to force them back in.
I cut off an old bit of seat post at a shallow angle to make a thin-wall but strong shoe-horn shape with a tip the same width as the front rail seat area. Locate the rear rail ends first then lever it in with the curved part of the lever facing the rail / back of the saddle, start with the lever at 90 deg to the saddle and push it back and down, may need to drift the rails along/down the lever face with a small hammer or add a smear of grease – the idea is that the rail moves down as you leverage it. It takes some force but if the lever is the right shape it’ll pop back in when the lever angle is shallower. Adult supervision + safety specs recommended.
(Edit to add, this makes me look either really tight, or a big fan of certain saddles that I have. Bit of both!)