Welcome to the QB! I had to upgrade my Grace Frame a few years ago with wooden track. I then purchased 2 long steel rods, bars, that were 115" long each to lay in the track. The metal bars, rods, work wonderfully and sit in that track perfect. You may want to do something like this. I have the original Grace Frame. I hope this helps a little. The plastic track becomes brittle after a short time which may be why they upgraded to the wood track. I also have the newer carriage it is well worth the money. My frame is showing its age now and I am struggling with keeping it in balance. The new parts should keep you going for the longest time.
Jump right in and join the fun.Again Welcome to the QB!