My only concern now that I have brought this to Matts attention is modifying the rear crossbar to except these slugs and that not be able to get the larger slugs in the future.
In the slim chance my theory is correct, which I can't prove or disprove at this point as our boat is an hour from the house, and the track has enlarged over time, and we (older or well used 18ers) who would want these "larger" slugs, are going to somehow insert them in the track. Whether this is using a dremil tool, removing the crossbar, heating it (I dont believe I said that) to get them in or pounding them in with a dowel, we will live with the fact our boats are old. There has always been the possibility of the car flying out the end of track, if you forget. So what have we lost or gained in comparison to the "right" sized components? In my opinion we have lost nothing, by a slight enlarging of the entry, and gained a tighter fit in the "usable" or most used part of the track.
And here's another point, how do we know this wasn't originally designed to be an interference fit, at the entry, in an attempt to keep the slug and ball in the track? In other words, designed to keep them captive after being initially "driven" in to the track.
Sell us the slugs...sell us the slugs...sell us the slugs