Ah, here is the mast issues.
I think you would be miles ahead to reuse your existing sail track. It's there, it's one piece made to fit for your mast. Filling the holes would be a good move if you slide the track up or down a bit because you want to get to new metal under it. What about removing just enough material to allow you to switch to machine threaded screws for the increased surface area? I have read of several people switching spar fasteners to machine thread for the increased surface area. I personally think our spars are just fine as far as attacments go because they are so heavily constructed relative to our boat. Arguably there is less surface area in the SM screws but it seems to be a moot point. It seems we should be more critical of our cast aluminum fittings instead of our fastenings.
The 18" track is for our OEM goose neck to slide on.
Yup, the Tides track slides right over our track and does exactly what you said. I personally hope that cracked track you refered to is a fluke and not the standard because I got one rolled up in the shop awaiting installation. The sail slides and batten cars were a fraction of the cost of some of the other systems we looked at. At the time, Joe Cooper at Hood was pleased with the Tides sysem and scored us a discount as part of the package price of a new set of sails. I don't have any personal experience with the Tides system other than moving it from one shop to another. I did ask Tim Lackey a bunch of questions before I got one and he spoke highly of it.
Forgot to mention it is made of UHMW plastic and the slides are stainless. The batten cars are stainless slides too. There is supposed to be considerably less friction travelling up AND down for the mainsail. Several people have claimed they no longer have to head-up to reef the main. I'm all about less stress though...