Following Gary's post I thought I'd check on my older boat. Having pulled the tramp off, I used a very bright torch to shine through the slot onto the inside of the track. Having thoroughly inspected both sides, I found a short crack (about 7" long) that had been repaired previously and was now ok - all of the rest of that port track and the entire starboard track were undamaged. I checked the integrity of the repaired crack by trying it with the blade of a penknife and I couldn't even get the tip in (I could have if I forced it, but you get the idea). I'm therefore perfectly content that enlarging the bolt rope was the correct solution and that the crack (repaired by a previous owner) was not contributing to the problem I was experiencing - especially as my tramp tended to pull out of the aft section of the starboard track!

Carl's right - I think you should look at the simpler solutions first................